NANOPARTICLES AND SYSTEMS AND METHODS FOR SYNTHESIZING NANOPARTICLES THROUGH THERMAL SHOCK
Systems and methods of synthesizing nanoparticles on substrates using rapid, high temperature thermal shock. A method involves depositing micro-sized particles or salt precursors on a substrate, and applying a rapid, high temperature thermal pulse or shock to the micro-sized particles or the salt precursors and the substrate to cause the micro-sized particles or the salt precursors to become nanoparticles on the substrate. A system may include a rotatable member that receives a roll of a substrate sheet having micro-sized particles or salt precursors; a motor that rotates the rotatable member so as to unroll consecutive portions of the substrate sheet from the roll; and a thermal energy source that applies a short, high temperature thermal shock to consecutive portions of the substrate sheet that are unrolled from the roll by rotating the first rotatable member. Some systems and methods produce nanoparticles on existing substrate. The nanoparticles may be metallic, ceramic, inorganic, semiconductor, or compound nanoparticles. The substrate may be a carbon-based substrate, a conducting substrate, or a non-conducting substrate. The high temperature thermal shock process may be enabled by electrical Joule heating, microwave heating, thermal radiative heating, plasma heating, or laser heating.
This application claims the benefit of and priority to U.S. Provisional Application No. 62/523,646, filed on Jun. 22, 2017, the entire contents of which are incorporated herein by reference.
BACKGROUND Technical FieldThis disclosure relates to nanoparticles synthesized or constructed on a substrate of interest through thermal shock, their methods of construction, and corresponding systems.
Related ArtThe synthesis of nanoparticles of metal and metal compounds has attracted a massive amount of attention because of their good catalytic activity. The conventional synthesis method—wet chemistry—involves complex chemical reactions where precise control of reaction conditions is required. This makes it challenging to synthesize uniform small-size nanoparticles. Moreover, uniformly dispersing nanoparticles on a substrate is even more challenging. Slight differences in reaction conditions can drastically change the morphology of the end product, which may be detrimental to the performance of the catalyst. This problem may become more severe and relevant when the catalyst has dimensions on the nanoscale level.
SUMMARYExisting challenges associated with the foregoing, as well as other challenges, are overcome by methods for synthesizing nanoparticles on a substrate, and also by systems and apparatuses that operate in accordance with these methods.
In aspects, this disclosure features a method of forming nanoparticles on a substrate. The method includes depositing micro-sized particles or salt precursors on a substrate, and applying a rapid, high temperature thermal shock to the substrate and the micro-sized particles or the salt precursors to cause the micro-sized particles or the salt precursors to self-assemble into nanoparticles on the substrate.
In another aspect, this disclosure features a system for synthesizing nanoparticles on a substrate. The system includes a rotatable member that receives a roll of a substrate sheet on which is deposited micro-sized particles or salt precursors, and a motor that rotates the rotatable member so as to unroll consecutive portions of the substrate sheet from the roll. The system also includes a thermal energy source, such as a thermal radiation source or a direct Joule heating source, that repeatedly applies a short, high temperature radiation pulse to consecutive portions of the substrate sheet that are unrolled from the roll by causing the motor to rotate the first rotatable member to cause the micro-sized particles or the salt precursors to self-assemble into nanoparticles on consecutive portions of the substrate sheet.
In yet another aspect, this disclosure features a composite, such as a film. The composite includes a substrate and a plurality of nanoparticles formed on the substrate from a micro-sized particle or salt precursors exposed to a rapid, high temperature thermal shock.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the disclosure and together with a general description of the disclosure given above, and the detailed description of the embodiment(s) given below, serve to explain the principles of the present disclosure.
Embodiments of the systems and methods of synthesizing nanoparticles on substrates are described in detail with reference to the drawings, in which like or corresponding reference numerals designate identical or corresponding elements in each of the several views.
This disclosure relates to low cost, simple, ultra-fast synthesis of nanoparticles for nanocatalysis, which is beneficial for the development of high performance nanocatalysts used for energy conversion and electrochemical processes, such as water splitting, fuel cells, metal air batteries, and other catalytic reactions, such as biomass conversion, ammonia oxidation, and so on.
The substrate may be a carbon-based substrate, a conducting substrate, or a non-conducting substrate. The carbon-based substrate may be a reduced graphene oxide substrate or a carbon nanofiber substrate. In some embodiments, the surface of the substrate may be treated to modify the wetting behavior and thereby change the nanoparticle size. For example, the surface of the substrate may be coated with an oxide coating by an atomic layer deposition (ALD) process or a solution process.
The RGO sheets work well as a host material because of their defect sites and high melting temperature. For example, the RGO sheets may be stable up to 3300 K. Thus, the micro-sized particles melt 125 upon heating and self-assemble into nanoparticles 120 due to the confinement by the defects 130 of the RGO sheet.
In embodiments, the substrate may be formed and the micro-sized particles may be deposited on or applied to the substrate to form a film according to any suitable procedures. For example, as illustrated by the method of
In some embodiments, the Hummer's method may be employed for the preparation of GO ink (block 902). First, a suspended solution of a mixture of natural graphite flakes (e.g., 1.5 g) and KMnO4 (e.g., 9 g) in acid of H2SO4/H3PO4 (e.g., 200 mL with a volume ratio 9:1) is prepared. For better dispersion, the solution may be heated (e.g., heated to 50° C.) while stirred continuously for an appropriate period (e.g., 12 hours). After achieving a uniform composition, the solution may be cooled down to room temperature before being poured onto ice (e.g., 200 mL) mixed with H2O2 (e.g., 3 mL). Subsequently, an HCl solution (e.g., a 100 mL 30% HCl solution) with a DI water bath may be used to wash away unwanted flakes. The resulting GO solution may have a concentration of 2.5 mg mL−1 after diluting it in distilled water.
Next, the Al-GO solution is prepared (block 904). The Al powders ink may be prepared by adding micro Al powders (e.g., 30 mg of 99.5%, Sigma-Aldrich) into ethanol (e.g., 12 mL), followed by sonication (e.g., 1 minute). The concentration of the prepared Al powders solution may be 2.5 mg/mL. The Al-GO solution may be prepared by mixing the as-prepared GO solution and Al powders solution with a weight of, for example, 1:1, followed by shaking (e.g., 1 minute) on a tube vertex mixer and then sonication (e.g., 10 seconds). Thus, a high quality Al-GO solution with GO sheets and monodispersed Al powders can be obtained since the GO sheets serve as a surfactant to disperse Al micro powders to form a uniform Al-GO suspension.
Next, the Al-GO film is prepared (block 906), e.g., via vacuum filtration. A freestanding Al-GO film (e.g., 35 mm in diameter) may be obtained by filtering the Al-GO solution (e.g., 6 mL) through a membrane (e.g., 0.65 μm pore-sized membrane). The film on the membrane is then dried in the air. The Al-GO film may then be detached from the membrane naturally. Then, the Al-GO film is reduced (block 905). Thermal pre-reduction of the Al-GO film may be carried out in a furnace. For example, thermal pre-reduction of the Al-GO film may be carried out in a tube furnace under H2/Ar (5%/95%) atmosphere, held at 300° C. for 10 min with a ramping rate of 5° C./min.
An appropriate structure, such as glass slides, may be prepared to hold the Al-RGO film. Two copper ribbons may be attached at each side of the glass mount, functioning as the connections to an external circuit and heat sinks. Silver paste may be applied to both ends of the Al-RGO film as electrodes, forming an Ohmic contact to the later annealed film. Then, a rapid, high temperature thermal shock is applied (block 910) to the Al-RGO film by applying a voltage across the two copper ribbons to synthesize Al nanoparticles on the RGO film.
In other embodiments, nanoparticles may be synthesized on substrates from salt precursors. The salt precursors may include or be made of metal chloride, metal nitrate, metal acetate, or any combination of these salt precursors.
In embodiments, salt precursors may be deposited on or in a CNF film to form a precursor-loaded film to be heated according to any suitable heating method. For example, nanoparticles dispersed on a film may be formed by preparing a film, depositing a salt precursor on the film to obtain a salt precursor-loaded film, and then applying a thermal shock to the salt precursor-loaded film.
In embodiments, a CNF film may be prepared according to the example method of
Next, a salt (e.g., PdCl2) is dissolved into a solution (e.g., water or ethanol) (block 806) and the resulting salt solution is deposited or applied into or onto the CNFs (e.g., by dipping, soaking, or vacuum filtration) (block 808) and dried (block 809). The resulting film (e.g., PdCl2-CNF film) is then exposed to rapid, high temperature thermal shock to synthesize nanoparticles (e.g., Pd nanoparticles) on the CNFs.
In the rapid heating process 412, in which the micro-FeS2-RGO film may be heated up to 2470 K, FeS2 powders decompose into Fe atoms 406 and S atoms 408. The Fe atoms 406 and S atoms 408 then diffuse 414 within the RGO matrix but remain in between the RGO layers under high temperature, thereby benefiting from the impermeability of RGO and the encapsulation effect of the RGO film. As rapid cooling 416 takes place, the Fe atoms 406 and S atoms 408 renucleate around the defects on the basal plane of the RGO nanosheets and crystallize into ultrafine FeS2 nanoparticles 410. The FeS2-RGO 3D nanostructure helps to maintain good mechanical integration and rapid electron transport of FeS2 nanoparticles embedded in the RGO nanosheets.
The methods of this disclosure enable in situ synthesis of FeS2 and other inorganic compound nanoparticles in an ultrafast, cost-effective, and scalable approach. FeS2 nanoparticles transformed from iron pyrite through ultrafast thermal shock can be used as catalysts to split water. Benefiting from the ultrafine FeS2 nanoparticles and the robust FeS2-RGO 3D structure, the as-synthesized nano-FeS2-RGO exhibits remarkable electrocatalytic performance for HER with, for example, only 139 mV overpotential to achieve 10 mA cm−2 current in 0.5 m H2SO4 solution for long-term operation. This strategy may also be applicable to synthesize other transition metal dichalcogenides and may be extended to ternary or multicomponent compounds.
In embodiments, CoS-RGO may be employed as an efficient bifunctional catalyst for both OER and HER simultaneously. As shown in
The electrocatalytic performance of CoS-RGO is attributed to the chemical composition and electronic structure of the synthesized CoS nanoparticles grown on N and S doped RGO nanosheets. Additionally, the N and S doping introduces defects on RGO nanosheets to form additional catalytic sites, and simultaneously induces the electronic interactions with nearby CoS nanoparticles, which are beneficial to enhance the catalytic performance for water splitting. The thin carbon coating on CoS active surface plays an important role in the corrosion resistance, resulting in impressive electrocatalytic stability.
In embodiments, the nanoparticles synthesized according to methods of this disclosure may be used in energy storage devices.
An example of the capacity retention of the RGO-Si nanoparticle electrode at 200 mA g−1 between 0.01 and 2.0 V is shown in
The performance of nanoparticles in the RGO matrix can be optimized by varying the process conditions. For example, the RGO functional groups can be altered, and the specific hold time and synthesis temperature can control the NP size.
The rapid, in situ synthesis of nanoparticles via high-temperature radiative heating can be scaled up by three-dimensional (3D) printing, e.g., by 3D printing RGO ribbons, as shown in the example image 711 of
The interaction between the nanoparticles and the substrates plays a role in determining the particle morphology, distribution, and properties. By tuning the wetting or interaction between the substrates and the nanoparticles, the design of nanoparticles with enhanced dispersion and controlled particle size may be achieved.
In embodiments, the surface modification can be achieved by coating of an additional layer on the substrates by gas phase, solution phase or solid phase reactions and processes. For example, atomic layer deposition (ALD) may be used to deposit oxide layers on the substrates. The surface modifications may also be achieved by surface treatment using gas phase, solution phase, or solid phase reactions or processes. For example, thermal annealing in a CO2 atmosphere may be performed to create surface defects.
Nanoparticles, and systems and methods for synthesizing nanoparticles from micro-sized particles or salt precursors on substrates in accordance with this disclosure are detailed above, as is the verification of these materials and methods through experimentation. Persons skilled in the art will understand that the features specifically described hereinabove and shown in the accompanying figures are non-limiting exemplary embodiments, and that the description, disclosure, and figures should be construed merely as exemplary of particular embodiments. It is to be understood, therefore, that the present disclosure is not limited to the precise embodiments described, and that various other changes and modifications may be effected by one skilled in the art without departing from the scope or spirit of the disclosure.
Claims
1-2. (canceled)
3. A method of forming nanoparticles on a substrate, the method comprising:
- depositing micro-sized particles or salt precursors on a substrate; and
- applying a rapid, high temperature thermal shock to the substrate and the micro-sized particles or the salt precursors to cause the micro-sized particles or the salt precursors to become nanoparticles on the substrate,
- wherein the micro-sized particles comprise aluminum, tin, gold, palladium, iron, nickel, silicon, or any combination thereof.
4-20. (canceled)
21. A system for synthesizing nanoparticles on a substrate, the system comprising:
- a rotatable member configured to receive a roll of a substrate sheet having deposited thereon micro-sized particles or salt precursors;
- a motor configured to rotate the rotatable member so as to unroll consecutive portions of the substrate sheet from the roll; and
- a thermal energy source configured to apply a short, high temperature thermal shock to consecutive portions of the substrate sheet that are unrolled from the roll by rotating the rotatable member to cause the micro-sized particles or the salt precursors to become nanoparticles on consecutive portions of the substrate sheet.
22. The system of claim 21, wherein the thermal energy source is a thermal radiation source or a direct Joule heating source.
23. The system of claim 21, further comprising a rotatable member configured to receive a roll for receiving a nanocomposite sheet comprising nanoparticles on consecutive portions of the substrate sheet.
24. A composite comprising:
- a substrate; and
- a plurality of nanoparticles formed on the substrate from a micro-sized particle or salt precursors exposed to a rapid, high temperature thermal shock.
25. The composite of claim 24, wherein the substrate is a reduced graphene oxide substrate for the micro-sized particles or a carbon nanofiber substrate for the salt precursors.
26. The composite of claim 24, wherein the micro-sized particles comprise aluminum, tin, gold, palladium, iron, nickel, silicon, or any combination thereof.
27. The composite of claim 24, wherein the salt precursors comprise metal chloride, metal nitrate, metal acetate, or any combination thereof.
28. The composite of claim 24, wherein the nanoparticles are metallic, ceramic, inorganic, semiconductor, compounds, or any combination thereof.
Type: Application
Filed: May 23, 2022
Publication Date: Nov 3, 2022
Inventors: Liangbing HU (Potomac, MD), Yanan CHEN (Hyattsville, MD), Yonggang YAO (College Park, MD)
Application Number: 17/750,577