Silicon photocathode functionalized with osmium complex catalyst for selective catalytic conversion of CO 2 to methane.

Solar-driven CO 2 reduction to yield high-value chemicals presents an appealing avenue for combating climate change, yet achieving selective production of specific products remains a significant challenge. We showcase two osmium complexes, przpOs, and trzpOs, as CO 2 reduction catalysts for selective CO 2 -to-methane conversion. Kinetically, the przpOs and trzpOs exhibit high CO 2 reduction catalytic rate constants of 0.544 and 6.41 s -1 , respectively. Under AM1.5 G irradiation, the optimal Si/TiO 2 /trzpOs have CH 4 as the main product and >90% Faradaic efficiency, reaching -14.11 mA cm -2 photocurrent density at 0.0 V RHE . Density functional theory calculations reveal that the N atoms on the bipyrazole and triazole ligands effectively stabilize the CO 2 -adduct intermediates, which tend to be further hydrogenated to produce CH 4 , leading to their ultrahigh CO 2 -to-CH 4 selectivity. These results are comparable to cutting-edge Si-based photocathodes for CO 2 reduction, revealing a vast research potential in employing molecular catalysts for the photoelectrochemical conversion of CO 2 to methane.