Interface engineering with an rGO electron extraction layer for high-efficiency and stable Cu2ZnSnS4-based photocathode

The practical application of Cu2ZnSnS4 (CZTS)-based photocathodes is hindered by severe charge recombination and insufficient charge transport capability. Herein, we demonstrate a high-performance Pt/reduced graphene oxide (rGO)/CdS/CZTS photocathode for solar hydrogen production by incorporating rGO nanosheets as an electron transport layer. The optimized photocathode achieves a photocurrent density of −21.73 mA/cm2 at 0 VRHE and an applied bias photon-to-current efficiency reaches 3.43%, representing 153% and 149% improvements over the control device without rGO, respectively. Furthermore, the incorporation of rGO boosts the charge separation efficiency from 94.89% to 99.07%, and the stability is significantly enhanced, maintaining performance over 10 h. Density functional theory calculations reveal the underlying electronic mechanism: the rGO interlayer facilitates efficient electron extraction from CdS and promotes charge exchange with Pt, thereby suppressing bulk recombination and enhancing interfacial charge transfer. This work provides useful insights into interface engineering of photocathodes for high-efficiency photoelectrochemical systems.