Defect-engineered oriented construction of S-scheme heterojunctions: Efficient photocatalytic performance of NiS-loaded TiO2 nanoflowers

Developing semiconductors with optimal bandgaps and enhancing their photocatalytic performance remain key challenges in achieving efficient hydrogen evolution from water splitting. TiO 2 nanoflowers with open architectures, which provide abundant active sites, show significant potential in this field. Additionally, the construction of photocatalysts using S-scheme heterojunctions has been proven to improve redox capacity, while the introduction of oxygen vacancies has been shown to increase efficiency. Therefore, in this study, NiS-loaded TiO 2 nanoflowers were fabricated by a simple template-free solvothermal method. Oxygen vacancies were constructed by partially reducing the composite with a low NiS concentration. The synergistic effect of the oxygen vacancies and heterojunctions greatly improved the visible-light response of the catalyst, and the degradation rate of rhodamine B reached 99.81 % in 3 h under visible light. The transient photocurrent response of 1.0 wt% NiS-TiO 2 nanoflowers was 47.52 μA·cm −2 and the rate of hydrogen evolution achieved 1782.28 μmol·g −1 ·h −1 , approximately 6.5 times higher than that of pristine TiO 2 nanoflowers. The transfer process of electrons was verified by calculation using density functional theory, and an electron transport mechanism for the S-scheme heterojunction is also proposed to illustrate the photocatalytic mechanism. The as-prepared NiS-loaded TiO 2 nanoflowers could be prime candidate for the photocatalytic hydrogen evolution from water splitting and degradation of organic pollutants.