Nonstoichiometric Sulfur Engineering in a 3D/0D NiTiO3/CuIn5S8 Heterojunction for Enhanced Photocatalytic Hydrogen Evolution

Modulating surface defects via sulfur engineering, combined with rational heterojunction design, represents a promising strategy to enhance the photocatalytic hydrogen evolution performance. This study presents a facile synthesis of CuIn5S8 quantum dots (CIS QDs) through sulfur engineering and their subsequent anchoring onto NiTiO3 (NTO) nanorods via a one-pot hydrothermal approach. The structural characterization revealed that the heterojunction possessed 2–6 nm CIS QDs, while NTO nanorods exhibited an average diameter of 361 nm and a length of 1.5–2.5 μm. Through comprehensive analysis, the excess S2– ions could form a passivation layer on the QD surfaces, which effectively suppressed surface defects and significantly improved charge separation efficiency. The optimized Z-scheme NTO/CIS-16S heterojunction achieved an exceptional hydrogen evolution rate of 22.7 mmol g–1 h–1, which surpasses most reported CIS- or NTO-based photocatalysts to date, representing 65.2- and 9.1-fold enhancements over pristine CIS-16S and NTO/CIS-1S, respectively. This work provides valuable insights into the construction of band-aligned heterojunctions and the regulation of interfacial charge dynamics, paving the way for efficient, solar-driven hydrogen production.