In Situ Reduction Fabricated Pt-Mediated Bi2WO6/g-C3N4 Heterojunction with Unconventional Z-Scheme Charge Transfer for Enhanced Photocatalysis and Hydrogen Evolution

Abstract

A novel Pt-mediated Z-scheme heterojunction photocatalyst, Pt-Bi₂WO₆/g-C₃N₄ (Pt-BWO/g-CN), was synthesized via an in situ reduction strategy, enabling precise Pt positioning as an electron mediator between BWO and g-CN. Structural and morphological analyses (FESEM, HRTEM, and BET) confirmed nanoscale integration, uniform Pt dispersion, and high surface area. X-ray photoelectron spectroscopy (XPS) revealed binding energy shifts indicative of efficient interfacial charge transfer, while UV–vis diffuse reflectance spectroscopy (DRS) and Mott–Schottky analyses confirmed favorable band alignment consistent with a direct Z-scheme pathway. Photoluminescence (PL) and photoelectrochemical measurements demonstrated suppressed electron–hole recombination and enhanced charge separation. Electron paramagnetic resonance (EPR) provided compelling mechanistic evidence: DMPO-trapped spectra detected abundant ^•OH and ^•O^2– radicals under light irradiation, TEMP-trapped spectra confirmed ¹O₂ formation, and intrinsic oxygen vacancies (g ≈ 2.003) were observed even in the dark, decreasing upon illumination, supporting defect-assisted charge transfer. The optimized Pt-BWO/g-CN achieved complete RhB degradation and 85% RR4 removal within 60 min under visible light, alongside a hydrogen generation rate of 5364.96 μmol g^–1 h^–1 (STH efficiency of 3.4% and AQY of 3.5%). Radical scavenging identified h⁺ and ^•O₂^– as the dominant active species. This work demonstrates a scalable route to high-performance Z-scheme photocatalysts with dual capability in pollutant degradation and solar hydrogen generation, underpinned by direct spectroscopic validation of the charge transfer pathway.