In Situ Reduction Fabricated Pt-Mediated Bi<sub>2</sub>WO<sub>6</sub>/g-C<sub>3</sub>N<sub>4</sub> Heterojunction with Unconventional Z-Scheme Charge Transfer for Enhanced Photocatalysis and Hydrogen Evolution
Nur Syamimi Adzis, Nur Hidayatul Syazwani Suhaimi, Rahil Azhar, Suriati Sufian, Mahidin Mahidin, Azhar Ali Haidry, Mohamad Fariz Mohamad Taib, Yee Hui Robin Chang, W.I. Nawawi, Mohd Azlan Mohd Ishak
Abstract
High Resolution Image Download MS PowerPoint Slide A novel Pt-mediated Z-scheme heterojunction photocatalyst, Pt-Bi 2 WO 6 /g-C 3 N 4 (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 1 O 2 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 • O 2 – 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.