Photoelectrochemical measurements for Sb2Se3 photocathodes: PEC performance of the Sb2Se3 photocathodes was measured in a three-electrode electrochemical cell with a potentiostat (BioLogic SP-300) under irradiation from simulated AM 1.5G illumination, calibrated using a silicon diode from PV Measurements, Inc. (100 mW cm -2 ). A Pt wire and an Ag/AgCl electrode (KOSLOW, saturated KCl) were used as the counter and reference electrode, respectively. The electrolyte used in PEC measurement for Sb2Se3 photocathodes was prepared by dissolving 0.5 M NaSO4 (Sigma Aldrich) and 0.1 M KH2PO4 (Sigma Adrich) in deionized water.