Unveiling the Selectivity of CO₂ Reduction on Cu₂ZnSnS₄: The Effect of Exposed Termination

Abstract

With the advantage of excellent light absorption ability and earth-abundant elements, Cu2ZnSnS4 (CZTS) is widely applied in the photoelectrochemical (PEC) reduction of CO2. However, the microscopic mechanism of the CO2 conversion on CZTS is still unclear. Here, we have theoretically investigated the electronic properties of the CZTS to reveal the special bonding properties of CO2 under both exposed metal and sulfur terminations of the CZTS and the formation mechanisms of producing CO, HCOOH, and CH4 from a microscopic perspective. Our study shows that when the metal is exposed to the surface, CO2 will convert to HCOOH with a high selectivity with the limiting potential of 0.23 V (vs RHE). However, on the sulfur termination, the onset potentials of producing HCOOH, CO, and CH4 are all lower than 0.4 V, indicating the mix formations. These findings provide theoretical insight into the PEC experiments of CO2 reduction on CZTS.