Nagakazu Furuya

Simultaneous reduction of carbon dioxide and nitrate ions at gas-diffusion electrodes with various metallophthalocyanine catalysts☆

Abstract Electrochemical conversion of carbon dioxide with nitrate ions into useful material consisting of CN bond under the mild condition has attracted much attention. Simultaneous reduction of CO 2 and nitrate ions was investigated at gas-diffusion electrodes with various metallophthalocyanine (MPc, M: Ti, V, Cr, Mo, Fe, Ru, Co, Ni, Pd, Cu, Zn, Cd, Ga, In, Ge, Sn and Pb) catalysts. The current efficiencies of CO formation at CoPc and NiPc catalysts in the reduction of CO 2 alone are extremely higher than that at metal catalysts, hence these MPc catalysts were expected to have a fairly high ability for urea formation. However, since the reduction of nitrate ions to nitrite ions and ammonia does not occur at the MPc catalysts, urea is not formed in the simultaneous reduction of carbon dioxide and nitrate ions. For the urea formation, it was confirmed that simultaneous generation of ammonia- and CO-like precursors at the catalysts was necessary.

Preparation of Gas Diffusion Electrodes by Electrophoretic Deposition

Gas diffusion electrodes were prepared by precipitates deposited from carbon-polytetrafluoroethylene dispersions using an electrophoretic deposition technique. The amount of the precipitate deposited on the oppositely charged electrode varied with the electrode substrate, suggesting that ions dissolved from the anode have the ability to coagulate particles. A cross-sectional analysis of the precipitate showed the profile of a functionally graded material. The ability of the gas diffusion electrode using Pt as a catalyst in alkaline solution to promote oxygen reduction and hydrogen oxidation was high. The H 2 -O 2 fuel cell in which the gas diffusion electrodes were used generated 0.77 V at 0.3 A/cm 2 .