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.