Enhanced photoelectrochemical catalysis of CO2 reduction mediated by a supramolecular electrode of packed CoII(tetrabenzoporphyrin)

A supramolecular electrode was made of stacked CoII(tetrabenzoporphyrin). The stack was held together by π–π interactions and the first layer of the porphyrin complex was anchored to the glassy carbon surface through the porphyrin’s 4-aminopyridine group. An electrode formed by CoII(tetrabenzoporphyrin) adsorbed on the glassy carbon surface was inactive towards the reduction of carbon dioxide. In contrast to this electrode, the supramolecular electrode exhibited good electrocatalytic activity towards the same reaction. Illumination of the supramolecular electrode enhanced its electrocatalytic activity towards the reduction of carbon dioxide. In the absence of the sensitizer, the illumination of the electrode with visible light induced an appreciable shift of the CO2 reduction wave towards more positive potentials. Also the shift of the wave was observed in experiments with the sensitizer, [Ru(bipy)3]3+, but in this case light of shorter wavelength had to be used.