Simultaneous Defect Passivation and Co‐catalyst Engineering Leads to Superior Photocatalytic Hydrogen Evolution on Metal Halide Perovskites

Abstract Metal halide perovskites (MHPs) have emerged as attractive candidates for producing green hydrogen via photocatalytic pathway. However, the presence of abundant defects and absence of efficient hydrogen evolution reaction (HER) active sites on MHPs seriously limit the solar‐to‐chemical (STC) conversion efficiency. Herein, to address this issue, we present a bi‐functionalization strategy through decorating MHPs with a molecular molybdenum‐sulfur‐containing co‐catalyst precursor. By virtue of the strong chemical interaction between lead and sulfur and the good dispersion of the molecular co‐catalyst precursor in the deposition solution, a uniform and intimate decoration of the MHPs surface with lead sulfide (PbS) and amorphous molybdenum sulfide (MoS x ) co‐catalysts is obtained simultaneously. We show that the PbS co‐catalyst can effectively passivate the Pb‐related defects on the MHPs surface, thus retarding the charge recombination and promoting the charge transfer efficiency significantly. The amorphous MoS x co‐catalyst further promotes the extraction of photogenerated electrons from MHPs and facilitates the HER catalysis. Consequently, drastically enhanced photocatalytic HER activities are obtained on representative MHPs through the synergistic functionalization of PbS and MoS x co‐catalysts. A solar‐to‐chemical (STC) conversion efficiency of ca. 4.63 % is achieved on the bi‐functionalized FAPbBr 3‐x I x (FA=CH(NH 2 ) 2 ), which is among the highest values reported for MHPs.