Pt-Loaded Z-Scheme g-C3N4/Bi4Ti3O12 Heterostructure for Enhanced Photocatalytic H2 Evolution

Efficient photocatalytic H2 evolution requires coordinated control of light absorption, interfacial charge transfer, and surface reduction kinetics. Here, g-C3N4/Bi4Ti3O12 (CN/BTO) heterojunctions were constructed by in-situ thermal coupling and subsequently modified through in-situ photodeposition of Pt. Among the investigated compositions, 2.5-CN/BTO showed the highest activity before Pt addition. Structural, optical, and electrochemical analyses indicate effective coupling between CN and layered BTO, while EPR measurements and band-position analysis are consistent with a direct Z-scheme charge-transfer pathway. Pt nanoparticles were found preferentially on CN-rich regions, supporting electron accumulation at the CN side of the heterostructure during photocatalysis. Pt incorporation increased the H2 production to 1278 μmol g−1 during the first 5 h, approximately 39 times that of pristine CN and BTO under the same conditions. Reuse tests revealed a pronounced loss of activity after the first cycle, followed by a slower decline, with H2 production of 360, 351, and 300 μmol g−1 over 5 h in cycles 2–4. Post-reaction analyses indicate structural and surface modification of the CN component, accompanied by localized Pt clustering, whereas the crystalline BTO phase remains largely preserved. The study therefore establishes the beneficial role of CN/BTO interfacial coupling and Pt cocatalysis in promoting H2 evolution, while revealing the structural evolution that limits sustained photocatalytic performance.