Electrochemical CO2 reduction was investigated on 32 metal electrodes in aqueous KHCO3 medium. The current efficiency of CO2 reduction on Ni, Ag, Pb, and Pd increases significantly with lowering the temperature. The ratio of reduction products are also changed by lowering temperature. Potential dependence of HCOOH and H2 on an Hg electrode supports the electron transfer mechanism for HCOOH production. Formation of methane and ethylene is observed on almost all metal electrodes used, although the efficiency is mainly very low except for Cu. A periodic table for CO2 reduction, which is drawn based on the dependence of reduction products on various metals, suggests the existence of a systematic rule for the electrocatalytic reduction of CO2 on metal surfaces.

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