Elucidation of the Synergistic Effect of Dopants and Vacancies on Promoted Selectivity for CO Electroreduction to Formate.

Sn-based materials are identified as promising catalysts for the CO electroreduction (CO2RR) to formate (HCOO ). However, their insufficient selectivity and activity remain grand challenges. A new type of SnO nanosheet with simultaneous N dopants and oxygen vacancies (V -rich N-SnO NS) for promoting CO conversion to HCOO is reported. Due to the likely synergistic effect of N dopant and V , the V -rich N-SnO NS exhibits high catalytic selectivity featured by an HCOO Faradaic efficiency (FE) of 83% at -0.9 V and an FE of > 90% for all C1 products (HCOO and CO) at a wide potential range from -0.9 to -1.2 V. Low coordination Sn-N moieties are the active sites with optimal electronic and geometric structures regulated by V and N dopants. Theoretical calculations elucidate that the reaction free energy of HCOO* protonation is decreased on the V -rich N-SnO NS, thus enhancing HCOO selectivity. The weakened H* adsorption energy also inhibits the hydrogen evolution reaction, a dominant side reaction during the CO2RR. Furthermore, using the catalyst as the cathode, a spontaneous Galvanic Zn-CO cell and a solar-powered electrolysis process successfully demonstrated the efficient HCOO generation through CO conversion and storage.