SELECTIVE ELECTROCATALYSIS FOR CO2 REDUCTION IN THE AQUEOUS-PHASE USING COBALT PHTHALOCYANINE/POLY-4-VINYLPYRIDINE MODIFIED ELECTRODES

The electrocatalytic reduction of CO2 in aqueous electrolytes by a cobalt phthalocyanine (CoPc)/poly-4-vinylpyridine (PVP) membrane coated on a graphite electrode was studied. Enhanced catalysis for CO2 electroreduction at more positive potential and of greater efficiency was achieved with the present system than with the system using pure CoPc as catalyst, whereas both coatings were found to catalyze proton reduction as well. The electrochemical behavior of the PVP-bound CoPc was examined at different pH, taking the normally adsorbed CoPc as reference. The greatly enhanced and sustained catalytic activity of the CoPc/PVP membrane for CO2 electroreduction in water is discussed in terms of electron donation of the pyridine group to the central cobalt by an axial coordination and a proton-exchanging property of the PVP and the increased local concentration of CO2 in the PVP layer owing to their hydrophobic and/or acid-base interaction. A reaction scheme for the electrocatalytic reduction of CO2 by CoPc is proposed.