Light-Induced Ultrafast Charge Transfer in Pt-Modified Cs ₂ PdBr ₆ for Efficient Electrocatalytic Hydrogen Evolution

Halide perovskites exhibit exceptional optoelectronic properties, including strong light absorption and efficient generation of photogenerated charge carriers. However, these advantages are extremely limited in electrocatalytic systems, and their full potential remains largely unexplored. In particular, the underlying mechanisms governing light-assisted electrocatalysis in perovskite materials remain poorly understood. Herein, a Pt-modified Cs 2 PdBr 6 all-inorganic halide perovskite (Cs 2 PdBr 6 @Pt 1.5 ) is designed, which achieves a low overpotential of 11 mV at 10 mA cm –2 with excellent water stability. Femtosecond transient absorption spectroscopy further demonstrates that the incorporation of Pt increases the population of transient species (<1 ps) and acts as an efficient charge separation channel, thereby promoting charge migration to catalytic active sites and enhancing hydrogen evolution reaction properties. Density functional theory (DFT) calculations reveal that electrons transfer from Cs 2 PdBr 6 to Pt, and Pt-modified Cs 2 PdBr 6 optimizes the adsorption energies of key reaction intermediates, thereby lowering the overpotential for water splitting. These findings highlight the potential of halide perovskites as a stable and efficient platform for light-assisted electrocatalytic water splitting and related energy conversion processes.