Construction of SnO2/g‑C3N4/TiO2 ternary Type-II heterojunctions for boosted photocatalytic hydrogen evolution

The narrow light-absorption range and fast charge carrier recombination in semiconductor photocatalysts remain major bottlenecks limiting photocatalytic hydrogen evolution efficiency. In this work, SnO 2 /g-C 3 N 4 /TiO 2 ternary Type-II heterojunctions were rationally constructed via a hydrothermal-calcination two step strategy. Triethanolamine (TEOA) was employed as a sacrificial agent during the photocatalytic hydrogen production reaction. Different from traditional simple component mixing, SnO 2 is deliberately designed as an electron mediator to bridge g-C 3 N 4 and TiO 2 , forming a directional cascade charge transfer channel for efficient carrier separation. DFT theoretical simulations further verify that the introduction of TiO 2 optimizes the band structure, reduces the work function, and promotes interfacial electron transfer, thus significantly enhancing photocatalytic performance. The optimized 0.20SnO 2 /g-C 3 N 4 /TiO 2 sample delivers a maximum H 2 evolution rate of 4.80 mmol/g/h, 2.38-fold higher than that of bare TiO 2 . Stability assessments confirmed the material's exceptional cycling durability, a characteristic primarily ascribed to the establishment of type II heterojunctions. This architectural configuration facilitates effective segregation and mobility of photoinduced charge carriers while simultaneously suppressing recombination of electron-hole pairs. The materials' superior photoelectrochemical characteristics further enhance their capacity for light-driven hydrogen generation through catalytic processes. These discoveries provide new perspectives and innovative approaches for engineering high-performance photocatalytic systems. • Type II SnO 2 /g-C 3 N 4 /TiO 2 heterojunction enhances charge transfer & light absorption. • 20% TiO 2 loading optimizes heterojunction interface and active site exposure. • Composite achieves 4.80 mmol·g -1 ·h -1 H 2 production with excellent cycling stability. • DFT confirms TiO2 improves semiconductor traits and aids charge separation.