Development of All-Solid-State Sputtered S‑Scheme Heterojunction Photoanode for Stable and Efficient Solar-Driven...

Scalable, clean hydrogen production via photoelectrochemical (PEC) water splitting is limited by poor light absorption and rapid charge recombination. Here, we report a rationally designed, all-solid-state plasmon-coupled S-scheme heterojunction photoanode, MoSe₂/Au/TiO₂, fabricated entirely through a scalable magnetron sputtering technique. The Initial MoSe₂/TiO₂ S-scheme heterojunction enhances light harvesting and achieves a photocurrent density of ∼0.25 mA/cm² at 1.23 V_rhe, supported by a surface photovoltage of 223 mV and a carrier lifetime of 0.2 s. The strategic introduction of an ultrathin Au interlayer profoundly modifies the interface. This Au mediator established a stronger built-in electric field, a more favorable band alignment, maintained high redox potentials, enhanced light absorption, and improved photo-charge separation with transfer. This engineered MoSe₂/Au/TiO₂ heterojunction photoanode delivers a markedly superior performance, with a photocurrent density of ∼0.54 mA/cm² at 1.23 V_rhe, a high surface photovoltage of 293.7 mV, and a prolonged carrier lifetime of 0.55 s, while maintaining stable operation over 6.5 h. Comprehensive experimental analysis, including in situ photoelectrochemical studies and spectroscopic characterization, systematically unveils the Au-mediated S-scheme mechanism, highlighting enhanced charge separation, reduced interfacial resistance, and preserved high redox potentials. This work establishes a scalable, robust S-scheme architecture for efficient solar-driven hydrogen generation.