Y Doped‐Induced Sulfur Vacancy‐Mediated Band/Fermi Level Coupling in in ₂ S ₃ for Efficient Pyro‐Photoelectrocatalytic Water Splitting Performance

ABSTRACT Pyro‐photoelectrocatalytic (Pyro‐PEC) water splitting integrates temperature fluctuations with solar irradiation to enable efficient hydrogen production, but conventional In 2 S 3 suffers from weak photoresponse, rapid carrier recombination, and poor band alignment, limiting practical applications. To address these limitations, herein we first design and fabricate sulfur vacancy‐mediated band bending and fermi level coupling V S ‐In 1.90 Y 0.10 S 3 electrode, for synergistically enhance Pyro‐PEC performance. Under Pyro‐PEC conditions, the V S ‐In 1.90 Y 0.10 S 3 electrode delivers a high current density of 2.79 mA cm −2 at 1.23 V vs. RHE, representing a 7.75‐fold improvement over In 2 S 3 , along with significantly enhanced operational stability. Notably, we first employ in situ pyro‐photoelectrochemical characterization to unveil that Y doped‐induced sulfur vacancies can drastically amplify interfacial band bending and built‐in electric field modulation under temperature fluctuations, thereby facilitating directed migration of photogenerated carriers and accelerating interfacial charge transfer. The performance enhancement originates from sulfur vacancy‐mediated regulation of local defect states and band structure in In 2 S 3 , which elevates the Fermi level, optimizes carrier transport and energy distribution, and enables the synergistic reinforcement of Pyro‐photoelectrocatalytic field effects under the combined stimuli of temperature fluctuation and photoexcitation. This work establishes a rare‐earth doping‐enabled defect engineering strategy, providing a novel material design paradigm and mechanistic insight for constructing high‐performance Pyro‐PEC hydrogen evolution electrodes.