Engineering S-scheme heterojunctions with multichannel charge transfer for efficient photocatalytic hydrogen production

Constructing efficient charge separation pathways remains a crucial challenge for advancing photocatalytic hydrogen evolution. In this work, a Ni2P/CdIn2S4/In2S3 (NP/CIS/IS) heterostructure featuring S-scheme charge separation and multiple electron transfer pathways was constructed through a stepwise assembly approach. Work function analysis, combined with in situ irradiated X-ray photoelectron spectroscopy (ISI-XPS) and density functional theory (DFT) calculations, confirmed the formation of a built-in electric field (BIEF) that drives directional carrier migration across the CIS/IS interface, establishing a typical S-scheme heterojunction. Electron paramagnetic resonance (EPR) studies further revealed significantly enhanced redox activity in the CIS/IS-3 system, attributed to the efficient spatial separation of photogenerated charges. The incorporation of NP nanoparticles remarkably boosted the visible-light-driven hydrogen evolution performance (λ ≥ 420 nm), achieving a high rate of 45,057.1 μmol g-1 h-1. This enhancement arises from the dual role of NP as the active site and electron mediator, facilitating charge extraction, lowering the Gibbs free energy for H2 formation, and accelerating hydrogen desorption. Furthermore, three-dimensional charge density mapping validated the presence of multiple synergistic charge transport channels within the 5.7%NP/CIS/IS-3 composite. This study provides new insights into the design of advanced heterostructured photocatalysts for efficient, sustainable hydrogen production from solar energy.