In2S3/TiO2 heterostructures for enhanced photocatalytic nitrogen fixation under ambient conditions

The development of sustainable routes for ammonia production under ambient conditions is a critical challenge, driven by the high energy demand and carbon footprint of the Haber-Bosch process. Photocatalytic N 2 fixation has emerged as a promising alternative; however, conventional TiO 2 -based systems suffer from rapid charge-carrier recombination, resulting in poor efficiency. Herein, we report the design of a noble-metal-free In 2 S 3 /TiO 2 heterostructure photocatalyst for photocatalytic N 2 fixation to NH 4 + under mild conditions. The coupling of TiO 2 nanoparticles with In 2 S 3 aims to promote charge carrier separation and suppress electron-hole recombination, thereby overcoming the intrinsic limitations of bare TiO 2 . Structural, morphological, optical, and electronic characterizations confirmed the successful formation of the heterojunction and the strong interfacial interaction between the two semiconductors. UV–Vis diffuse reflectance spectroscopy revealed an extended light absorption toward the visible region, while photoluminescence and XPS analyses evidenced enhanced charge separation and interfacial charge redistribution. Among the investigated compositions, the In 2 S 3 (10%)/TiO 2 sample exhibited the best photocatalytic performance, achieving an NH 3 production of 214.0 μmol·g cat −1 after 3 h of irradiation, significantly higher than pristine TiO 2 . Experimental and DFT investigations demonstrated the formation of a type-II heterojunction, promoting electron migration from In 2 S 3 to TiO 2 and suppressing electron-hole recombination. The combined experimental and theoretical results highlight the potential of noble-metal-free In 2 S 3 /TiO 2 heterostructures as efficient photocatalysts for sustainable N 2 fixation under ambient conditions.