Unveiling the potential of ZnIn2S4/γ-Al2O3 heterojunction for cocatalyst-free hydrogen generation and high-performance supercapacitors

Advancing renewable energy technologies necessitates photocatalysts that synergistically integrate exceptional efficiency with environmental sustainability. This study presents a rationally designed novel ZnIn2S4/γ-Al2O3 nanocomposite, wherein γ-Al2O3 transcends its conventional passive-support role to actively modulate charge carrier dynamics through surface electrostatic effects, enabling bifunctionality in visible-light-driven photocatalytic hydrogen evolution and electrochemical energy storage. Comprehensive characterization via PXRD, UV–Vis DRS, FE-SEM, HR-TEM, XPS, BET, TG-DTA, CV, GCD, EIS, and Mott-Schottky analyses confirmed the formation of an electronically integrated heterointerface with high surface area, diminished charge-transfer resistance, and favourable interfacial band alignment. The 10 % ZnIn2S4/γ-Al2O3 nanocomposite achieved a remarkable hydrogen evolution rate of 1172 μmol g−1 h−1 under visible light without cocatalyst, substantially surpassing pristine ZnIn2S4. This enhancement originates from a surface-potential-driven electrostatic charge separation mechanism, wherein negatively charged Al-O- surface groups and defect-induced trap states within non-photoactive γ-Al2O3 create localized interfacial field that facilitates spatial charge separation and dual-pathway hole scavenging. Concurrently, the nanocomposite delivered superior supercapacitor performance, exhibiting a specific capacitance of 450 F g−1 at 1 A g−1, with corresponding energy and power densities of 56.25 Wh kg−1 and 892 W kg−1, respectively. This synergistic integration positions ZnIn2S4/γ-Al2O3 as a compelling dual-functional platform for integrated solar energy conversion and electrochemical storage.