Engineering the interfacial electric field in a NiSnO3/g-C3N4 S-scheme heterojunction for efficient photocatalytic hydrogen production and CO2 reduction.

Green synthesis of 2D S-scheme NiSnO 3 /g-C 3 N 4 heterojunction photocatalyst. • Interfacial field and N-vacancies promote efficient charge separation. • Bandgap narrowing with visible-NIR light absorption confirmed by UV-Vis. • Achieved 3963 μmol g −1 h −1 H 2 evolution and 78 μmol g −1 h −1 CO 2 reduction. • Stable, scalable, and multifunctional photocatalyst for solar energy conversion. Efficient solar-driven hydrogen generation and carbon dioxide conversion are key to renewable energy and environmental remediation. Here, a porous NiSnO 3 /g-C 3 N 4 (NSO/CN) S-scheme heterojunction with engineered nitrogen vacancies and a strong interfacial electric field, yielding exceptional photocatalytic performance. The NSO/0.5-CN composite exhibits a high specific surface area and a narrowed bandgap, promoting broad visible-light absorption and abundant active sites. Charge-carrier studies confirm spatially separated electron-hole transfer via an S-scheme mechanism. As a result, hydrogen evolution reaches 3854.7 with standard deviation (SD) 108.9 µmol g −1 h −1, over five times the rate of pristine NiSnO 3, and CO 2 reduction attains 74.53 with SD 3.5 µmol g −1 h −1 , far surpassing either component alone. The strong built-in field and Nitrogen-vacancies inhibit recombination and increase redox activity, resulting in consistent performance and complete dye degradation. This study uses defect engineering and an S-scheme design to demonstrate that NiSnO 3 /g-C 3 N 4 can be engaged as a photocatalyst to generate renewable energy, utilise CO 2 , and clean up pollutants. The computational study imparts support to the innovative findings and reveals a novel method for creating multifunctional nanostructures using a green water bath. Download: Download high-res image (174KB) Download: Download full-size image The graphical abstract illustrates the S-scheme heterojunction with enhanced charge separation for multi-functional photocatalysis.