Advances in molecular photocatalytic and electrocatalytic CO2 reduction

This review describes recent developments in photocatalytic and electrocatalytic CO2 reduction. On the electrocatalytic side, there have been advances in optimization of known rhenium motifs sometimes in conjunction with silicon photoelectrodes giving enhanced catalytic current and stability. Complexes of copper capable of absorbing atmospheric CO2 have been incorporated into an electrocatalytic cycle and metal-free electrocatalysis of CO2 to methanol has been achieved with pyridinium ions. A complete cell with two photo-electrodes, one for water oxidation and the other for CO2 reduction to formate has been set up successfully. The cathode employs ruthenium catalysts on InP. Progress in photocatalytic CO2 reduction has been made with osmium complexes exhibiting good selectivity and stability. The separation between Ru and Re centers in light-harvesting donor–acceptor dyads has been investigated providing some inspiration for design. A ruthenium catalyst has been sensitized by tantalum oxide particles. Metalloporphyrin-rhenium dyads have also been studied for photocatalytic CO2 reduction. In the biological arena, a ruthenium complex has been used to sensitize carbon monoxide dehydrogenase on titanium dioxide particles.

► Development of electrocatalysts that absorb atmospheric CO2.
► Electrocatalysts are composed of earth-abundant materials, some totally organic.
► Photocatalytic CO2 reduction is coupled to water oxidation.
► CO2 reducing enzymes are powered by visible light.
► Low energy visible light is harvested by porphyrins and utilized for CO2 reduction.