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

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 CO2 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 CO2 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. (C) 2003 Elsevier Ltd. All rights reserved.