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According to one embodiment of a CO 2 reduction catalyst of the present invention, a conductive material is immersed in an aqueous solution containing a gold source, and a current or a potential is applied, whereby a highly active CO 2 reduction catalyst can be formed in a wide range portion on a surface of the conductive material. According to one embodiment of a CO 2 reduction catalyst of the present invention, in a CO 2 reduction reaction apparatus including a CO 2 reduction electrode having the CO 2 reduction catalyst, CO 2 is reduced.
1. A CO 2 reduction catalyst precipitated and formed by electrodeposition, wherein said CO 2 reduction catalyst is equipped with a porous metal layer, the porous metal layer including an aggregate, wherein the aggregate is formed by aggregating fine particles having a primary particle diameter of not less than 10 nm and not more than 200 nm and has a secondary particle diameter of not less than 200 nm and not more than 10 μm, or the porous metal layer including a site where fine particles having a particle diameter of not less than 10 nm and not more than 200 nm are deposited to a height of not less than 30 nm, or the porous metal layer including both the aggregate and the site, and the porous metal layer has a site, which electrically reduces CO 2 , at least a portion of a surface thereof.
2. The CO 2 reduction catalyst according to claim 1 , further comprising a thiol derivative.
3. The CO 2 reduction catalyst according to claim 1 , wherein in the porous metal layer, a ratio ({111}/{100}) between a maximum value of peak strength deriving from a {111} plane and a maximum value of peak strength deriving from a {100} plane in X-ray diffraction measurement is not less than 2.0.
4. The CO 2 reduction catalyst according to claim 1 , further comprising a surfactant.
5. A CO 2 reduction electrode comprising a conductive material and the CO 2 reduction catalyst according to claim 1 having conductivity with the conductive material.
6. The CO 2 reduction electrode according to claim 5 , comprising a porous structure or a through hole.
7. A CO 2 reduction reaction apparatus comprising:
an oxidation electrode which oxidizes water;
the CO 2 reduction electrode according to claim 5 ;
a power supply element which have electric conductivity with the oxidation electrode and the CO 2 reduction electrode; and
an electrolytic solution in contact with the oxidation electrode and the CO 2 reduction electrode.
8. A process for producing the CO 2 reduction catalyst according to claim 1 , comprising:
immersing a conductive material in an aqueous solution containing a metal source and a surfactant; and
applying a constant reduction current to precipitate the CO 2 reduction catalyst on the conductive material.
9. A process for producing the CO 2 reduction catalyst according to claim 1 , comprising:
immersing a conductive material in an aqueous solution containing a metal source and an electrolyte; and
precipitating the CO 2 reduction catalyst on the conductive material.