Abstract: Iron compound particles comprise a ?-FeOOH crystal phase and a metal element other than Fe with which the ?-FeOOH crystal phase is doped, wherein the metal element other than Fe is at least one metal element selected from the group consisting of elements of Al as well as 3d and 4d transition metals belonging to periodic table Groups 4 to 12 other than Fe, an atomic ratio of the metal element other than Fe to the Fe element (metal element other than Fe/Fe element) is 0.001 to 0.5, and the iron compound particles satisfy at least one of the following requirements (A) and (B): (A) having a crystallite diameter of 1 to 60 nm when measured by X-ray diffraction; and (B) having an average particle diameter of 1 to 600 nm when measured by dynamic light scattering in a solvent.

Abstract: Iron compound particles comprise a ?-FeOOH crystal phase and a metal element other than Fe with which the ?-FeOOH crystal phase is doped, wherein the metal element other than Fe is at least one metal element selected from the group consisting of elements of Al as well as 3d and 4d transition metals belonging to periodic table Groups 4 to 12 other than Fe, an atomic ratio of the metal element other than Fe to the Fe element (metal element other than Fe/Fe element) is 0.001 to 0.5, and the iron compound particles satisfy at least one of the following requirements (A) and (B): (A) having a crystallite diameter of 1 to 60 nm when measured by X-ray diffraction; and (B) having an average particle diameter of 1 to 600 nm when measured by dynamic light scattering in a solvent.

Abstract: To provide a photocatalyst having high selectivity and carrying out a reductive reaction with light having a longer wavelength. A photocatalyst has a structure in which a semiconductor and a substrate are joined, in which the substrate causes a catalytic reaction by transfer to the substrate of excited electrons, which are generated by applying light to the semiconductor.

Abstract: The present invention provides: an oxidation reaction electrode that generates oxygen by oxidizing water; and a reduction reaction electrode that synthesizes a carbon compound by reducing carbon dioxide. The two electrodes are electrically connected. Also, the reduction reaction electrode (1) synthesizes a carbon compound by reducing carbon dioxide in a water-containing liquid using radiated light energy.

Abstract: To provide a photocatalyst having high selectivity and carrying out a reductive reaction with light having a longer wavelength. A photocatalyst has a structure in which a semiconductor and a substrate are joined, in which the substrate causes a catalytic reaction by transfer to the substrate of excited electrons, which are generated by applying light to the semiconductor.