ELECTROPLATING SOLUTION FOR MANUFACTURING NANOMETER PLATINUM AND PLATINUM BASED ALLOY PARTICLES AND METHOD THEREOF

The present invention generally relates to an electroplating solution for manufacturing nanometer platinum and platinum based alloy particles and a method thereof. That is, an acid solution having platinum complex compound and citric acid is provided into a reaction tank to be as an electroplating solution, then a plurality of platinum and platinum based alloy particles are deposited on the surfaces of electrodes under the condition of applying negative potentials. The acid solution is capable of effectively providing the rate of conducting ions. The citric acid can effectively promote the dispersity of the platinum and platinum based alloy particles and reduce the dimensions the platinum and platinum based alloy particles.

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Description
BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to an electroplating solution for manufacturing nanometer platinum and platinum based alloy particles and a method thereof, more particularly to that adding citric acid into the electroplating solution in order to nanometerize the platinum and platinum based alloy particles deposited on the surfaces of electrodes, and diffuse them averagely.

2. Description of the Prior Art

At present, the world relies on fossil energy that is the main source of energy, but limited oil reserves. After five decades, oil production capacity will be inadequate, it can be expected that a human energy crisis will be encountered in the near future. High oil prices impact the livelihood of people and the brunt of industry, such as everything from industrial use, home use of electricity, transportation dynamic energy, consumer electronics, mobile communications products, etc., which are all the needs of “energy” supply. At present, regardless of our government or the international community are constantly looking for alternative energy programs, it is the use of other alternative energy sources for the delay. Hydrogen is one of the most promising new energy source, and the use of fuel cells is the most important way of hydrogen, which can be divided into low-temperature fuel cell proton exchange membrane fuel cell (proton exchange membrane fuel cell, PEMFC), and direct methanol fuel cells (direct methanol fuel cell, DMFC), which can be operated below 100° C. For the portion of portable energy, due to that the functions of consumer electronic products are ever-increasing and the requirements of the batteries are continuously upgraded as well, such as lightweight, high-energy density, durability, convenience, etc. Hence, the low-temperature fuel cells replacing the lithium batteries are now highly expected.

Since PEMFC uses the electrochemical reaction of hydrogen and oxygen, it is natural and very concerned about environmental protection. Additionally, DMFC cooperates with the development of PEM (proton exchange membrane), so that the direction (towards low-power) of application and the direction of research and development of DMFC have revolutionized. Compared to the hydrogen-fed) of PEMFC, the power density of DMFC is significantly smaller, the best known for power density is still only one-tenth more than the former. Since the power density of DMFC is not so high, the application scope can be one of the following group consisting of laptop computer, PDA, cellular phone, etc. The typical MEA (membrane electrode assembly) of DMFC includes PEM, electrode catalyst layer and gas diffusion layer, wherein the gas diffusion layer can also be defined an electronic conductive layer. DMFC is a device that directly converts the chemical energy of liquid methanol to electrical energy at the temperature of 100° C. PEMFC uses hydrogen to be as a source of fuel. Recently, the most problem to DMFC is the low conversion efficiency thereof, so current research may focus on the development of high activity electrode catalyst.

The known theoretical voltage to DMFC at the temperature of 298° K., and the voltage can be obtained by following two electrochemical half-cell reaction equations:

For the anode half-cell reaction equation,


CH3OH +H2O→CO2+6H++6e−, wherein E°anode=0.05 VSHE,

For the cathode half-cell reaction equation,


3/2O2+6H+6e−→3H2O, wherein E°cathode=1.23 VSHE

Above anode electrochemical reaction and cathode electrochemical reaction use metal catalysts to lower energy barrier in order to accelerate oxidation reaction (anode) and reduction reaction (cathode). For the plurality of precious metal catalysts, Pt has the best activity to the oxidation of anode fuel (methanol) and the reduction of cathode fuel (oxygen). Hence, Pt is mainly a material of electrode catalyst in research.

To promote the efficiency of anode, the mechanism to processing the reactions may be understood firstly. Therefore, general half-cell reaction equations are listed below:


Pt+CH3OH→Pt—COad+4H+4e−  (a)


H2O+Pt→Pt—OH+H++e−  (b)


Ru+H2O→Ru—OH+H++e−  (c)


Pt—CO+Ru—OH→Pt+Ru+CO2+H+e−  (d)


Pt—COad+Pt—OHad→CO2+H++e−  (e)


Pt—CHOad+Ru—OHad→CO2+2H++2e−  (f)

Firstly, methanol may be sucked on the surface of Pt, then a plurality of steps of eliminating protons generate CO, which is sucked on the surface of Pt, as shown in equation (a). There is very strong bonding between Pt and CO so as to cause that the surface of Pt is occupied by CO. Gradually, the activity position for proceeding a catalytic reaction is reduced, that is, the surface of Pt is reduced, and thus the power of a cell is definitely down. It is called CO poisoning. If adding Pt—Ru catalyst to proceed the catalytic reaction, a type of alloy Pt—Ru may effectively improve the phenomenon of the CO position. The steps for the improvement are of: the activation of Ru and H2O producing Ru—OH, as shown in equation (c), then Ru—OH being provided to adjacent Pt—COad for the oxidation of CO in order to produce CO2 and proceed destorption, as shown in equation (d), if the product is Pt—CHOad, a similar reaction being made and then destorption being proceeded as well, as shown in equation (f). As it can be seen, to develop a platinum based alloy catalyst for promoting the efficiency of the oxidation of the methanol of the anode is the most important issue to the skilled people.

Additionally, for the cathode of DMFC, the oxidation of the methanol at the anode produces CO2, protons, and electrons. The power energy is provided while the produced electrons move from the anode to the cathode through an external circuit. Continuously, the produced electrons react with the protons diffused to the cathode through PEM and the fuel (oxyien) of the cathode to reduce a product, H2O, mostly Pt metal is the catalyst. Wherein the reasons to cause the worse electrochemical activity of the catalyst of the cathode can be shown as following half-cell reaction equations:


O2+4H++4e−=H2O, and  (g)


E°298° K.=+1.23 VSHE


O2+2H++2e−=H2O2,  (h)


E°298° K.=+0.68 VSHE,


Pt+H2O=Pt—O+2H++2e−, and


E°298° K.=+0.88 VSHE

In the oxidation-reproduction into water process of the cathode of DMFC, the reduction of partial oxyien produces H2O2, as shown in equation (h), and the oxidation of the surface of Pt happens while the condition is a higher potential, as shown in equation (i), the voltage loss of the cathode reduction of DMFC may then be more than 0.3 V. Further, for the problem of methanol crossover, presently there are many improvement ways as to make PEM thicker, add one more layer of pure carbon powder or platinum based alloy catalyst in order to decrease the speed of penetration of methanol. Such ways also increase the junction impedance of DMFC so as to lower down the efficiency of a fuel cell, that is, the development of DMFC is seriously blocked.

Generally speaking, for promoting the catalyst activity of DMFC, a catalyst with higher dispersion and small dimensions may have a characteristic of better activity. There are two most improvement ways, which include that of: (1) a nanometer carbon support carrying a catalyst to promote the dispersion of the catalyst; and (2) changing the structure of the catalyst, such as using a two-platinum-based alloy or ternary alloy to be as for a catalyst. More, a nanometer catalyst can also promote the specific surface area in order to increase a surface touching with fuel, that is, the utilization of the catalyst is increased as well. Hence, a result for above mentions is that developing a brand new nanometer platinum based alloy catalyst to promote the reaction efficiency of oxidizing methanol and reducing oxygen into water is the most important issue to the skilled people in the art.

Nowadays, there are two ways to manufacture low-temperature fuel cell catalyst electrodes mostly, one is chemical reduction, the other one is electroplating.

The chemical reduction includes the steps of: to immerse carbon carrier into a salt-alcohol water solution for a couple of hours, wherein the salt-alcohol water solution includes platinum and other transition metals as tungsten, ruthenium, cobalt, iron, nickel, etc.; drying the carbon carrier in a room temperature; and heating the carbon carrier in a 250-300° C. furnace with the gas of argon or hydrogen; or adding the gas of hydrogen into the water solution for several hours; and platinum metal or nanometer platinum based alloy particles being deposited on the carbon carrier. Basically, for chemical reduction, the pH value of a solution should be controlled in order to benefit the progress of reduction-oxidation-reduction. Besides, the temperature should be between 60° C. and 50° C. Although depositing a single metal as platinum in chemical reduction is existing for a period of time, which is not short, adding neutralizer as sodium hydroxide (NaOH) or potassium hydroxide (KOH) may be necessary in deposition. Further, the chemical reduction takes longer time and sodium ions and potassium ions are deposited on the carbon carrier simultaneously so as to cause additional pollutions.

In addition, using electroplating to deposit particles of a single metal or several metals is to put metal precursors, which will be deposited, as complex compound salt to be as an acidity solution of an ionized solution, wherein the complex compound salt is one of the following: Sulfuric acid (H2SO4), nitric acid (HNO3), perchloric acid (HlO4), perchloric acid hydrogen (HCl), etc. And a potential is applied to a conductive substrate, wherein the potential is normally negative. Hence, the substrate itself is negatively charged at cathode, a corresponding electrode is normally a non-polarizable electrode, such as platinum, and positively charged at anode. Electron exchange between ions in the solution and the substrate is thus happening, so that the deposition is made. However, the use of electroplating making metal particle size is usually 20 nm or more, that would make the surface area of the catalyst significantly lower, and in the field of catalytic chemistry, it will be a considerable obstacle.

SUMMARY OF THE INVENTION

According to aforesaid, the inventor of the present invention has spent lots of time for development, so that an electroplating solution for manufacturing nanometer platinum and platinum based alloy particles and a method thereof are then generated.

The primary objective of the present invention is to provide the electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles and the method thereof. That is, an acid solution having citric acid with a suitable concentration is provided to be as an electroplating solution while in an electroplating process. The citric acid is both a dispersant and a stabilizer and nanometerizes the platinum and platinum based alloy particles deposited on the surfaces of electrodes under the condition of not affecting the oxidation reaction of platinum and transition metal complex compound on the surfaces of the electrodes, wherein the oxidation reaction is the reduction of metal ions, and a better dispersity is achieved in order to break through a bottle neck that the catalyst metal particles in the electroplating process cannot be nanometerized. Such that, the application of the catalyst electrodes of a fuel cell can maximized.

The secondary objective of the present invention is to provide the electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles and the method thereof. That is, an acid solution having citric acid and lactic acid with a suitable concentration is provided to be as an electroplating solution while in an electroplating process. The citric acid is both a dispersant and a stabilizer and nanometerizes the platinum and platinum based alloy particles deposited on the surfaces of electrodes under the condition of not affecting the oxidation reaction of platinum and transition metal complex compound on the surfaces of the electrodes, wherein the oxidation reaction is the reduction of metal ions, and a better dispersity is achieved in order to break through a bottle neck that the catalyst metal particles in the electroplating process cannot be nanometerized. Such that, the application of the catalyst electrodes of a fuel cell can maximized.

The third objective of the present invention is to provide the electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles and the method thereof. That is, an acid solution having citric acid and boric acid with a suitable concentration is provided to be as an electroplating solution while in an electroplating process. The citric acid is both a dispersant and a stabilizer and nanometerizes the platinum and platinum based alloy particles deposited on the surfaces of electrodes under the condition of not affecting the oxidation reaction of platinum and transition metal complex compound on the surfaces of the electrodes, wherein the oxidation reaction is the reduction of metal ions, and a better dispersity is achieved in order to break through a bottle neck that the catalyst metal particles in the electroplating process cannot be nanometerized. Such that, the application of the catalyst electrodes of a fuel cell can maximized.

The fourth objective of the present invention is to provide the electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles and the method thereof. That is, an acid solution having citric acid and sulfuric acid with a suitable concentration is provided to be as an electroplating solution while in an electroplating process. The citric acid is both a dispersant and a stabilizer and nanometerizes the platinum and platinum based alloy particles deposited on the surfaces of electrodes under the condition of not affecting the oxidation reaction of platinum and transition metal complex compound on the surfaces of the electrodes, wherein the oxidation reaction is the reduction of metal ions, and a better dispersity is achieved in order to break through a bottle neck that the catalyst metal particles in the electroplating process cannot be nanometerized. Such that, the application of the catalyst electrodes of a fuel cell can maximized.

The fifth objective of the present invention is to provide the electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles and the method thereof. That is, an acid solution having citric acid and glycol with a suitable concentration is provided to be as an electroplating solution while in an electroplating process. The citric acid is both a dispersant and a stabilizer and nanometerizes the platinum and platinum based alloy particles deposited on the surfaces of electrodes under the condition of not affecting the oxidation reaction of platinum and transition metal complex compound on the surfaces of the electrodes, wherein the oxidation reaction is the reduction of metal ions, and a better dispersity is achieved in order to break through a bottle neck that the catalyst metal particles in the electroplating process cannot be nanometerized. Such that, the application of the catalyst electrodes of a fuel cell can maximized.

The sixth objective of the present invention is to provide the electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles and the method thereof. That is, an electroplating solution having at least citric acid is provided into a reaction tank, continuously a suitable cathode and anode are selected, and then a suitable potential is applied, so that the best nanometer platinum and platinum based alloy particles can be made.

Other and further features, advantages, and benefits of the invention will become apparent in the following description taken in conjunction with the following drawings. It is to be understood that the foregoing general description and following detailed description are exemplary and explanatory but are not to be restrictive of the invention. The accompanying drawings are incorporated in and constitute a part of this application and, together with the description, serve to explain the principles of the invention in general terms. Like numerals refer to like parts throughout the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects, spirits, and advantages of the preferred embodiments of the present invention will be readily understood by the accompanying drawings and detailed descriptions, wherein:

FIG. 1 illustrates the steps of a method for manufacturing nanometer platinum and platinum based alloy particles of the present invention;

FIG. 2 illustrates a schematic top view of a reaction tank of the present invention;

FIG. 3 illustrates a schematic sectional view of the reaction tank of the present invention;

FIG. 4 illustrates a plurality of micro films of a scanning electron microscopy and a transmission electron microscopy of depositing Pt on a nanotube sampler C-P (a), a nanotube sampler H-P (b), a nanotube sampler PC-P (c), and a nanotube sampler PH-P (d) of the present invention;

FIG. 5 illustrates a plurality of micro films of the scanning electron microscopy and the transmission electron microscopy of a nanotube sampler C-PR (a) and a nanotube sampler PC-PR (b) and the scanning electron microscopy of a nanotube sampler H-PR (c) and a nanotube sampler PH-PR (d) of the present invention;

FIG. 6 illustrates a plurality of micro films of the scanning electron microscopy of a nanotube sampler CD26-03 (a), a nanotube sampler CD26-20 (b), a nanotube sampler CD28-01 (c), a nanotube sampler CD28-02 (d), and a nanotube sampler CD28-09 (e) of the present invention; and

FIG. 7 illustrates a plurality of micro films of the scanning electron microscopy of samplers 0115 (a), 0118 (b) and 0219 (c) of the present invention.

 DETAILED DESCRIPTION OF THE INVENTION

Following preferred embodiments and figures will be described in detail so as to achieve aforesaid object.

To achieve aforesaid, the present invention discloses a method for manufacturing nanometer platinum and platinum based alloy particles in a solution with citric acid via an electroplating process. That is, a mixture having a solution with citric acid or another solution with citric acid mixed with other acids is added into an electroplating solution, which is applied in an electroplating process, the concentrations of the citric acid and the other acids may then be repeatedly tested and amended. Following with a first preferred embodiment of the ingredients of an electroplating solution, a second preferred embodiment of the ingredients of an electroplating solution, a third preferred embodiment of the ingredients of an electroplating solution, a fourth preferred embodiment of the ingredients of an electroplating solution, a fifth preferred embodiment of the ingredients of an electroplating solution, and a preferred method of an electroplating process of the present invention will be described.

Firstly, the first preferred embodiment of the ingredients of the electroplating solution for the method of manufacturing the nanometer platinum and platinum based alloy particles in the solution with the citric acid via the electroplating process includes: a solution having a platinum metal complex compound, the concentration of the platinum metal complex compound in the electroplating solution is between 0.1 micron molarity (0.1×10−6 M) and 100 molarity (M); and an acid solution having citric acid, the concentration of the citric acid in the electroplating solution is between 0.01 molarity (M) and 5 molarity (M); wherein the electroplating process can be progressed while the electroplating solution achieves a certain temperature that is between 18° C. and 60° C.

The first preferred embodiment of the ingredients of the electroplating solution can be further added a non-platinum metal complex compound, which comprises one of the group consisting of: the elements of the group B in the periodic table, Bismuth, Magnesium, Iridium, and Tin, wherein the concentration of the non-platinum metal complex compound in the electroplating solution is between 0.1 micron molarity (0.1×10−6 M) and 100 molarity (M).

Secondly, the second preferred embodiment of the ingredients of the electroplating solution for the method of manufacturing the nanometer platinum and platinum based alloy particles in the solution with the citric acid via the electroplating process includes: a solution having a platinum metal complex compound, the concentration of the platinum metal complex compound in the electroplating solution is between 0.1 micron molarity (0.1×10−6 M) and 100 molarity (M); and an acid solution having citric acid and lactic acid, the concentration of the citric acid in the electroplating solution is between 0.01 molarity (M) and 5 molarity (M), the concentration of the lactic acid in the electroplating solution is between 0.005 molarity (M) and 10 molarity (M); wherein the electroplating process can be progressed while the electroplating solution achieves a certain temperature that is between 18° C. and 60° C. .

The second preferred embodiment of the ingredients of the electroplating solution can be further added a non-platinum metal complex compound, which comprises one of the group consisting of: the elements of the group B in the periodic table, Bismuth, Magnesium, Iridium, and Tin, wherein the concentration of the non-platinum metal complex compound in the electroplating solution is between 0.1 micron molarity (0.1×10−6 M) and 100 molarity (M).

Thirdly, the third preferred embodiment of the ingredients of the electroplating solution for the method of manufacturing the nanometer platinum and platinum based alloy particles in the solution with the citric acid via the electroplating process includes: a solution having a platinum metal complex compound, the concentration of the platinum metal complex compound in the electroplating solution is between 0.1 micron molarity (0.1×10−6 M) and 100 molarity (M); and an acid solution having citric acid and boric acid, the concentration of the citric acid in the electroplating solution is between 0.01 molarity (M) and 5 molarity (M), the concentration of the boric acid in the electroplating solution is between 0.005 molarity (M) and 10 molarity (M); wherein the electroplating process can be progressed while the electroplating solution achieves a certain temperature that is between 18° C. and 60° C. .

The third preferred embodiment of the ingredients of the electroplating solution can be further added a non-platinum metal complex compound, which comprises one of the group consisting of: the elements of the group B in the periodic table, Bismuth, Magnesium, Iridium, and Tin, wherein the concentration of the non-platinum metal complex compound in the electroplating solution is between 0.1 micron molarity (0.1×10−6 M) and 100 molarity (M).

Fourthly, the fourth preferred embodiment of the ingredients of the electroplating solution for the method of manufacturing the nanometer platinum and platinum based alloy particles in the solution with the citric acid via the electroplating process includes: a solution having a platinum metal complex compound, the concentration of the platinum metal complex compound in the electroplating solution is between 0.1 micron molarity (0.1×10−6 M) and 100 molarity (M); and an acid solution having citric acid and sulfuric acid, the concentration of the citric acid in the electroplating solution is between 0.01 molarity (M) and 5 molarity (M), the concentration of the sulfuric acid in the electroplating solution is between 0.005 molarity (M) and 10 molarity (M); wherein the electroplating process can be progressed while the electroplating solution achieves a certain temperature that is between 18° C. and 60° C. .

The fourth preferred embodiment of the ingredients of the electroplating solution can be further added a non-platinum metal complex compound, which comprises one of the group consisting of: the elements of the group B in the periodic table, Bismuth, Magnesium, Iridium, and Tin, wherein the concentration of the non-platinum metal complex compound in the electroplating solution is between 0.1 micron molarity (0.1×10−6 M) and 100 molarity (M).

Fifthly, the fifth preferred embodiment of the ingredients of the electroplating solution for the method of manufacturing the nanometer platinum and platinum based alloy particles in the solution with the citric acid via the electroplating process includes: a solution having a platinum metal complex compound, the concentration of the platinum metal complex compound in the electroplating solution is between 0.1 micron molarity (0.1×10−6 M) and 100 molarity (M); and an acid solution having citric acid and glycol, the concentration of the citric acid in the electroplating solution is between 0.01 molarity (M) and 5 molarity (M), the concentration of the glycol acid in the electroplating solution is between 0.005 molarity (M) and 10 molarity (M); wherein the electroplating process can be progressed while the electroplating solution achieves a certain temperature that is between 18° C. and 60° C. .

The fifth preferred embodiment of the ingredients of the electroplating solution can be further added a non-platinum metal complex compound, which comprises one of the group consisting of: the elements of the group B in the periodic table, Bismuth, Magnesium, Iridium, and Tin, wherein the concentration of the non-platinum metal complex compound in the electroplating solution is between 0.1 micron molarity (0.1×10−6 M) and 100 molarity (M).

With reference to FIG. 1, which illustrates the steps of the method for manufacturing the nanometer platinum and platinum based alloy particles of the present invention. The steps are of: (102) formulating an electroplating solution having at least a solution with a platinum metal complex compound and at least an acid solution with citric acid, and then enabling the electroplating solution to achieve a certain temperature, wherein the electroplating solution is selected from the group consisting of the first, second, third, fourth, and fifth preferred embodiments and not described any further, the electroplating solution being achieved to a temperature between 18° C. and 60° C.; (103) loading the formulated electroplating solution into a reaction tank, selecting a conductive member/semi-conductive member to be as a cathode, which is a working electrode, and a platinum metal to be as an anode, which is a counter electrode; (104) disposing a reference electrode into the reaction tank, wherein the reference electrode is selected from the group consisting of: saturated calomel electrode, silver/chloride electrode and standard hydrogen electrode; and (105) applying a potential to the cathode for a certain period of time in order to manufacture the nanometer platinum and platinum based alloy particles, wherein the potential is selected from the group consisting of: pulsed DC and non-pulsed DC, the potential scope of the pulsed DC being between 1 VSHE and −2 VSHE, wherein the potential scope is corresponding to the standard hydrogen electrode potential, the frequency scope of the pulsed DC being between 0.1 micro HZ and 1000 KHZ, the potential scope of the non-pulsed DC being between 0.0 VSHE and −2 VSHE, wherein the potential scope is corresponding to the standard hydrogen electrode potential as well, the applying time for the pulsed DC and the non-pulsed DC being between 1 ms and 24 hours.

Please refer to FIG. 2 and FIG. 3, which illustrate a schematic top view of the reaction tank of the present invention and a schematic sectional view of the reaction tank of the present invention. As shown in the figures, the arrangements from the outside to inside of the reaction tank are the reaction tank 201, the anode (counter electrode) 202, the cathode (working electrode) 204, a supporting cathode tube 205, a supporting reference electrode tube 206, and the reference electrode 207, and the electroplating solution 203 is in the reaction tank 201.

A three-electrode electro chemical system as a preferred embodiment adopts a saturated calomel electrode (SCE) as a reference electrode, a platinum metal as a working electrode and a carbon nanotube sampler as a working electrode. The preferred embodiment is that the Pt nanocatalyst, Pt—Ru nanocatalyst and Pt—Co nanocatalyst are respectively deposited on the carbon nanotube sampler (working electrode). There are two ways to apply electroplating potential, and the two ways are a pulsed DC potential and a non-pulsed DC potential (fixed potential). The pulsed DC potential is +0.0 VSCE corresponding to saturated calomel electrode potential and −1.20 VSCE. The frequency of applied potential is 5 Hz (+0.0 VSCE) and 1 Hz (−1.20 VSCE). The non-pulsed DC potential, fixed potential, is −1.2 VSCE. The metal precursors of the preferred embodiment are platinum chloride acid, H2PtCl6.6H2O, ruthenium chloride, RuCl3.xH2O, and cobalt chloride (CoCl2.6H2O). The concentration in aqueous solution of added citric acid monohydrate is between 0.01-0.15 molarity (pH=1.9-2.2). The aqueous solution of sulfuric acid (H2SO4) is selected to be as a supported solution of the electroplating solution for comparison. Further, other mixed solutions as citric acid and boric acid, citric acid and lactic acid, citric acid and clycol acid, and citric acid and sulfuric acid are to be as different electroplating solutions for comparison. Table 1 is for the conditions of preparing the Pt nanocatalyst, Pt—Ru nanocatalyst and Pt—Co nanocatalyst and listed below:

platinum chloride acid ruthenium cobalt Supported solution No. concentration chloride chloride (molarity) potential C-P 0.2 mM — — citric acid (0.15 M) fixed potential H-P 0.2 mM — — sulfuric acid (0.01 M) fixed potential PC-P 0.2 mM — — citric acid (0.15 M) pulsed DC potential PH-P 0.2 mM — — sulfuric acid (0.01 M) pulsed DC potential C-PR 0.2 mM 0.8 mM — citric acid (0.15 M) fixed potential H-PR 0.2 mM 0.8 mM — sulfuric acid (0.01 M) fixed potential PC-PR 0.2 mM 0.8 mM — citric acid (0.15 M) pulsed DC potential PH-PR 0.2 mM 0.8 mM — sulfuric acid (0.01 M) pulsed DC potential CD26-03 0.2 mM —  3 mM citric acid (0.01 M) pulsed DC boric acid(0.01 M) potential CD26-20 0.2 mM — 40 mM citric acid (0.01 M) pulsed DC boric acid(0.01 M) potential CD28-01 0.2 mM — — citric acid (0.01 M) pulsed DC lactic acid (0.05M) potential CD28-02 0.2 mM 0.8 mM — citric acid (0.01 M) pulsed DC lactic acid (0.05M) potential CD28-09 0.2 mM 0.8 mM — citric acid (0.15 M) pulsed DC glycol(0.25 M) potential 0115 0.2 mM — — citric acid (0.15 M) pulsed DC sulfuric acid (0.01 M) potential 0118 0.5 mM — — citric acid (0.15 M) pulsed DC sulfuric acid (0.1 M) potential 0219 0.5 mM — — citric acid (0.3 M) pulsed DC sulfuric acid (0.1 M) potential

Before starting electroplating, removing oxygen in an electroplating solution can be by way of nitrogen or argon, and the conditions are under a normal pressure and the temperature of 30° C. De-ionized water can then be used to wash the prepared catalyst electrodes. Through the oxidation reaction of such metal precursors (H2PtCl6.6H2O.RuCl3.xH2O.CoCl2.6H2O) on the surfaces of the electrodes, the Pt nanocatalyst, Pt—Ru nanocatalyst and Pt—Co nanocatalyst are deposited on the electrodes of nanotubes, which are Pt/CNTs/CC, Pt—Ru/CNTs/CC and Pt—Co/CNT/CC.

With reference to FIG. 4, which illustrates a plurality of micro films of a scanning electron microscopy and a transmission electron microscopy of depositing Pt on a nanotube sampler C-P (a), a nanotube sampler H-P (b), a nanotube sampler PC-P (c), and a nanotube sampler PH-P (d) of the present invention. Wherein, the selected metal precursor is platinum chloride acid (H2PtCl6.6H2O). The supported solution for the nanotube sampler C-P (a) and the nanotube sampler PC-P (c) is citric acid (C6H8O7.H2O); more, the supported solution for the nanotube sampler H-P (b) and the nanotube sampler PH-P (d) is sulfuric acid (H2SO4), and the concentrations are shown in table 1. Additionally, the potential for the nanotube samplers C-P (a) and H-P (b) is fixed potential; and the potential for the nanotube samplers PC-P (c) and PH-P (d) is pulsed DC potential. In FIG. 4, the white particles in the left micro films of the scanning electron microscopy and the black particles in the right films of the transmission electron microscopy are Pt particles. Under the condition of the electroplating of the fixed potential, the particle diameter of the Pt particle mounted on the sampler C-P (a) made by adding citric acid to be as a supported solution, is between 3 and 6 nm, then it is more average than the particle diameter of the Pt particle mounted on the sampler H-P (b) made by adding sulfuric acid to be as a supported solution. In view of the left micro film of the scanning electron microscopy of the sampler H-P (b), the Pt particles made by adding sulfuric acid to be as a supported solution are aggregated obviously, and the diameter of the Pt particle is between 50 and 300 nm. For the aspect of pulsed DC potential, the particle diameter of the Pt particle mounted on the sampler PC-P (C) made by adding citric acid to be as a supported solution is more average than the particle diameter of the Pt particle of the sampler PH-P (d) made in sulfuric acid aqueous solution. Further, each of the samplers C-P (a) and PC-P (c) is selecting citric acid to be as a supported solution, wherein the distribution density of the Pt particles of the sampler PC-P (c) made by the way of pulsed DC potential is better than the sampler C-P (a). Therefore, it is known that the distribution density and diameter of the Pt particle made by adding citric acid as a supported solution are better than the Pt particle made by sulfuric acid. Which means, citric acid is able to play the roles of electrolyte for ion conduction and dispersant for forming nanometer metal particles simultaneously. More, the Pt particles made by the way of pulsed DC potential have the features of better metal distribution and smaller particle on the surfaces of CNTs (carbon nanometer tube). A better activity can be expected while such Pt catalyst with above two features is applied to the field of low-temperature fuel cell.

With reference to FIG. 5, which illustrates a plurality of micro films of the scanning electron microscopy and the transmission electron microscopy of a nanotube sampler C-PR (a) and a nanotube sampler PC-PR (b) and the scanning electron microscopy of a nanotube sampler H-PR (c) and a nanotube sampler PH-PR (d) of the present invention. The four samplers show that Pt—Ru particles are deposited on the CNTs by way of the present invention, and the metal precursors as platinum chloride acid (H2PtCl6.6H2O) and ruthenium chloride (RuCl3.xH2O) are added into an electroplating solution simultaneously. The supported solution for the samplers C-PR (a) and PC-PR (b) is citric acid, and sulfuric acid is for the samplers H-PR(c) and PH-PR (d). The concentrations are shown in table 1. The potential for the samplers C-PR (a) and H-PR (c) is fixed potential, and The potential for the samplers PC-BR (b) and PH-PR (d) is pulsed DC potential. To compare the Pt—Ru nanometer catalyst particle of the samplers C-PR (a) and PC-PR (b) made by adding citric acid as a supported solution and the Pt—Ru nanometer catalyst particle of the samplers H-PR (c) and PH-PR (d) made by adding sulfuric acid as a supported solution, it is obvious that the Pt—Ru catalyst metal made by adding sulfuric acid as a supported solution is shaped as a thin film mostly, that is, the metal averagely wrap around the surfaces of the CNTs. Such appearance is formed by metallic aggregation, and a smaller catalyst surface will happen; on the other hand, the Pt—Ru nanometer catalyst particles made by adding citric acid as a supported solution are shaped as round balls mostly, which diameter is between 3 and 6 nm. Then, it is knowing that the Pt—Ru nanometer catalyst particles made by adding citric acid as a supported solution is able to play the roles of electrolyte for ion conduction and dispersant for forming nanometer metal particles simultaneously. Further that, the Pt—Ru nanometer catalyst particles of the sample PC-PR (b) made by the same supported solution (citric acid) and the way of pulsed DC potential have better dispersity on the surfaces of the CNTs, therefore the Pt—Ru nanometer catalyst particles of the sampler C-PR (a) made by the way of fixed potential is worse.

With reference to FIG. 6, which illustrates a plurality of micro films of the scanning electron microscopy of a nanotube sampler CD26-03 (a), a nanotube sampler CD26-20 (b), a nanotube sampler CD28-01 (c), a nanotube sampler CD28-02 (d), and a nanotube sampler CD28-09 (e) of the present invention. Wherein the contents of the mixed solution for the samplers CD26-03 (a) and CD-26-20 (b) are citric acid and boric acid, and the mixed solution is as an electroplating solution; the contents of the mixed solution for the samplers CD28-01 (c) and CD-28-02 (b) are citric acid and lactic acid, and the mixed solution is as an electroplating solution; the contents of the mixed solution for the samplers CD28-09 (e) are citric acid and glycol, and the mixed solution is as an electroplating solution. For the samplers CD26-03 (a) and CD26-20 (b), both use the mixed solution of the same concentrations of citric acid and boric acid, different concentrations of cobalt chloride and the same concentrations of platinum chloride acid to prepare Pt—Co nanometer particles, wherein the concentrations of cobalt chloride of the samplers CD26-03 (a) and CD26-20 (b) are 3 mM and 40 mM respectively. For the samplers Cd28-01 (c) and CD28-02 (d), both use the mixed acidity solution of citric acid and lactic acid to prepare Pt and Pt—Ru nanometer particles respectively. As shown in FIG. 6, both of the supported solutions of 0.01-M citric acid and 0.05-M lactic acid can prepare Pt and Pt—Ru nanometer particles as well. The sampler CD28-09 (e) adopts the mixed solution of citric acid and glycol to be as an electrode solution in order to prepare Pt—Ru nanometer particles, as shown in FIG. 6.

With reference to FIG. 7, which illustrates a plurality of micro films of the scanning electron microscopy of samplers 0115 (a), 0118 (b) and 0219 (c) of the present invention. With the conditions of the mixed acidity solution of 0.15-M citric acid and 0.01-M sulfuric acid and 0.2-mM platinum chloride acid, Pt nanometer particles are made, as shown on the sampler 0115 (a). With the same concentrations of citric acid and sulfuric acid and 0.5-mM platinum chloride acid, Pt nanometer particles can also be made, as shown on the sampler 0118 (b). It represents that changing the concentration of Pt metal precursor may not affect the dimensions of prepared particles. At last, under the conditions of fixing 0.5-nM platinum chloride acid, promoting the concentration (0.1 M) of sulfuric acid, and different concentrations of citric acid (0.15-M sampler 0118 (b) and 0.3-M sampler 0219 (c)), such Pt nanometer particles are prepared. As shown in FIG. 7, changing the concentration of citric acid may manufacture Pt nanometer particle while promoting the concentration of sulfuric acid. As a conclusion, no matter the concentration and cooperated acidity solution or alcohol solution (glycol), the nanometer particles of Pt, Pt—Co, and Pt—Ru can be made under adding citric acid.

Nowadays, micro power generators are important to mobile electronic devices, such as laptop computer, digital camera, PDA, cellular phone, etc. As it can be seen, traditional chargeable batteries are heavy, therefore the convenience is very limited. Continuously, some substituted power generators are being developed. One of them, called MFC (direct methanol fuel cell), is not only that satisfying the demand of fast charging, but also that providing convenience. DMFC is a power-generating device that directly converts the chemical energy of methanol to electrical energy. The advantages for using methanol are light weight, slim volume, longer time, easy changing fuel, and lower contamination. Therefore, methanol becomes an important option for the next generation of micro-power supply system. However, the supported catalyst volume for fuel cell is still high presently. For example, the most effect of the fuel cell using methanol should be at least 2 mg/cm2 of supported catalyst volume. And the cost of precious metals is still high so as to cause that the cost to develop fuel cell can not be lowered down to consumer demands. So that, providing a catalyst with a lower supported catalyst volume and a catalytic efficiency is the most important issue in the field of low-temperature fuel cell.

The present invention mainly provides a new electroplating method for manufacturing a nanometer catalyst. Some features are mentioned as below. Adding glycol into the electroplating solution makes the particles of a catalyst to be diffuse averagely. Glycol can be a stabilizer, and cannot make the aggregation of particles so as to nanometerize the particles. Such particles can lower down the supported catalyst volume and promote the utilization of the catalyst, which means, the electrochemical reaction efficiency is raised so as to highly promote the whole performance of a fuel cell. The present invention avoids the waste of the cost to manufacture the fuel cell due to a lot of consumption of the catalyst as well.

According to the situations of international oil continuously being raised and green environmentally-friendly energy being developed, the development of new energy around the world has become a common goal. Fuel cells which have the high-energy flow due to density, high conversion efficiency, low pollution and other characteristics of a great deal of attention as a new energy development technologies. In particular, the recent feature for portable electronic products is derived from insufficient battery power, and energy added to bring the issue of environmental protection, fuel cells have a relatively high power rechargeable battery life can be added at any time, as well as the advantages of low pollution and can be hope a new generation of energy technologies in the main flow. In the short-term, fuel cells into the main fuel flow future are expected to have a huge demand for electricity. Therefore, the development of the outcome of the present invention will help to accelerate the pace of commercialization of the direct methanol fuel cell.

Claims

1. An electroplating solution for manufacturing nanometer platinum and platinum based alloy particles comprising:

a solution having a platinum metal complex compound; and
an acid solution having citric acid;
wherein an electroplating process can be progressed while the electroplating solution achieves a certain temperature.

2. The electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles according to claim 1, wherein the concentration of the platinum metal complex compound in the electroplating solution is between 0.1 micron molarity (0.1×10−6 M) and 100 molarity (M).

3. The electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles according to claim 1 further comprising a non-platinum metal complex compound, which comprises one of the group consisting of: the elements of the group B in the periodic table, Bismuth, Magnesium, Iridium, and Tin.

4. The electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles according to claim 3, wherein the concentration of the non-platinum metal complex compound in the electroplating solution is between 0.1 micron molarity (0.1×10−6 M) and 100 molarity (M).

5. The electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles according to claim 1, wherein the concentration of the citric acid in the electroplating solution is between 0.01 molarity (M) and 5 molarity (M).

6. The electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles according to claim 1, wherein the certain temperature of the electroplating solution is between 18° C. and 60° C..

7. An electroplating solution for manufacturing nanometer platinum and platinum based alloy particles comprising:

a solution having a platinum metal complex compound; and
an acid solution having citric acid and lactic acid;
wherein an electroplating process can be progressed while the electroplating solution achieves a certain temperature.

8. The electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles according to claim 7, wherein the concentration of the platinum metal complex compound in the electroplating solution is between 0.1 micron molarity (0.1×10−6 M) and 100 molarity (M).

9. The electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles according to claim 7 further comprising a non-platinum metal complex compound, which comprises one of the group consisting of: the elements of the group B in the periodic table, bismuth, magnesium, iridium, and tin.

10. The electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles according to claim 9, wherein the concentration of the non-platinum metal complex compound in the electroplating solution is between 0.1 micron molarity (0.1×10−6 M) and 100 molarity.

11. The electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles according to claim 7, wherein the concentration of the citric acid in the electroplating solution is between 0.01 molarity (M) and 5 molarity (M).

12. The electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles according to claim 7, wherein the concentration of the lactic acid in the electroplating solution is between 0.005 molarity (M) and 10 molarity (M).

13. The electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles according to claim 7, wherein the certain temperature of the electroplating solution is between 18° C. and 60° C..

14. An electroplating solution for manufacturing nanometer platinum and platinum based alloy particles comprising:

a solution having a platinum metal complex compound; and
an acid solution having citric acid and boric acid;
wherein an electroplating process can be progressed while the electroplating solution achieves a certain temperature.

15. The electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles according to claim 14, wherein the concentration of the platinum metal complex compound in the electroplating solution is between 0.1 micron molarity (0.1×10−6 M) and 100 molarity (M).

16. The electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles according to claim 14 further comprising a non-platinum metal complex compound, which comprises one of the group consisting of: the elements of the group B in the periodic table, Bismuth, Magnesium, Iridium, and Tin.

17. The electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles according to claim 16, wherein the concentration of the non-platinum metal complex compound in the electroplating solution is between 0.1 micron molarity (0.1×10−6 M) and 100 molarity (M).

18. The electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles according to claim 14, wherein the concentration of the citric acid in the electroplating solution is between 0.01 molarity (M) and 5 molarity (M).

19. The electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles according to claim 14, wherein the concentration of the boric acid in the electroplating solution is between 0.005 molarity (M) and 10 molarity (M).

20. The electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles according to claim 14, wherein the certain temperature of the electroplating solution is between 18° C. and 60° C..

21. An electroplating solution for manufacturing nanometer platinum and platinum based alloy particles comprising:

a solution having a platinum metal complex compound; and
an acid solution having citric acid and sulfuric acid;
wherein an electroplating process can be progressed while the electroplating solution achieves a certain temperature.

22. The electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles according to claim 21, wherein the concentration of the platinum metal complex compound in the electroplating solution is between 0.1 micron molarity (0.1×10−6 M) and 100 molarity (M).

23. The electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles according to claim 21 further comprising a non-platinum metal complex compound, which comprises one of the group consisting of: the elements of the group B in the periodic table, Bismuth, Magnesium, Iridium, and Tin.

24. The electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles according to claim 23, wherein the concentration of the non-platinum metal complex compound in the electroplating solution is between 0.1 micron molarity (0.1×10−6 M) and 100 molarity (M).

25. The electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles according to claim 21, wherein the concentration of the citric acid in the electroplating solution is between 0.01 molarity (M) and 5 molarity (M).

26. The electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles according to claim 21, wherein the concentration of the sulfuric acid in the electroplating solution is between 0.005 molarity (M) and 10 molarity (M).

27. The electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles according to claim 21, wherein the certain temperature of the electroplating solution is between 18° C. and 60° C.

28. An electroplating solution for manufacturing nanometer platinum and platinum based alloy particles comprising:

a solution having a platinum metal complex compound; and
an acid solution having citric acid and glycol;
wherein an electroplating process can be progressed while the electroplating solution achieves a certain temperature.

29. The electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles according to claim 28, wherein the concentration of the platinum metal complex compound in the electroplating solution is between 0.1 micron molarity (0.1×10−6 M) and 100 molarity (M).

30. The electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles according to claim 28 further comprising a non-platinum metal complex compound, which comprises one of the group consisting of: the elements of the group B in the periodic table, Bismuth, Magnesium, Iridium, and Tin.

31. The electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles according to claim 30, wherein the concentration of the non-platinum metal complex compound in the electroplating solution is between 0.1 micron molarity (0.1×10−6 M) and 100 molarity (M).

32. The electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles according to claim 28, wherein the concentration of the citric acid in the electroplating solution is between 0.01 molarity (M) and 5 molarity (M).

33. The electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles according to claim 28, wherein the concentration of the glycol in the electroplating solution is between 0.005 molarity (M) and 10 molarity (M).

34. The electroplating solution for manufacturing the nanometer platinum and platinum based alloy particles according to claim 28, wherein the certain temperature of the electroplating solution is between 18° C. and 60° C.

35. A method for manufacturing nanometer platinum and platinum based alloy particles comprising the steps of:

(1) formulating an electroplating solution having at least a solution with a platinum metal complex compound and at least an acid solution with citric acid, and then enabling the electroplating solution to achieve a certain temperature;
(2) loading the formulated electroplating solution into a reaction tank, selecting a conductive member/semi-conductive member to be as a cathode, which is a working electrode, and a platinum metal to be as an anode, which is a counter electrode;
(3) disposing a reference electrode into the reaction tank; and
(4) applying a potential to the cathode for a certain period of time in order to manufacture the nanometer platinum and platinum based alloy particles.

36. The method for manufacturing nanometer platinum and platinum based alloy particles according to claim 35, wherein the electroplating solution of step (1) achieves a temperature between 18° C. and 60° C..

37. The method for manufacturing nanometer platinum and platinum based alloy particles according to claim 35, wherein the reference electrode of step (3) is selected from the group consisting of: saturated calomel electrode, silver/chloride electrode and standard hydrogen electrode.

38. The method for manufacturing nanometer platinum and platinum based alloy particles according to claim 35, wherein the potential of step (4) is selected from the group consisting of: pulsed DC and non-pulsed DC.

39. The method for manufacturing nanometer platinum and platinum based alloy particles according to claim 38, wherein the potential range of the pulsed DC is between 1 VSHE and −2 VSHE, the frequency range of the pulsed DC is between 0.1 Hz and 1000 Hz, wherein the potential range of the pulsed DC is equivalent to the standard hydrogen electrode potential.

40. The method for manufacturing nanometer platinum and platinum based alloy particles according to claim 38, wherein the potential range of the non-pulsed DC is between 0.0 VSHE and −2 VSHE, wherein the potential range of the non-pulsed DC is equivalent to the standard hydrogen electrode potential.

41. The method for manufacturing nanometer platinum and platinum based alloy particles according to claim 35, wherein the time period of applying the potential of step (5) is between 1 ms and 24 hours.

Patent History
Publication number: 20100176001
Type: Application
Filed: Nov 27, 2009
Publication Date: Jul 15, 2010
Applicant: NATIONAL TSING HUA UNIVERSITY (TAIWAN) (Hsinchu)
Inventors: Chuen-Horng Tsai (Hsinchu), Ming-Chi Tsai (Hsinchu), Tsung-Kuang Yeh (Hsinchu)
Application Number: 12/626,877
Classifications
Current U.S. Class: Powder, Flakes, Or Colloidal Particles (205/74)
International Classification: C25D 1/00 (20060101); B22F 9/00 (20060101);