Novel p–n heterojunctions incorporating NiS1.03@C with nitrogen doped TiO2 for enhancing visible-light photocatalytic performance towards cyclohexane oxidation

Highlights: • The NiS_1.03@C/N-TiO₂ catalyst was prepared via solvothermal plus annealing approach. • A promising cyclohexane conversion and selectivity were achieved under visible light. • The N-doping and p-n heterojunction facilitate the separation of electrons-holes. • The carbon promote the adsorption of cyclohexane and desorption of oxidation products. Herein, p-n heterojunction photocatalysts incorporating NiS_1.03@C with nitrogen doped TiO₂ (NiS_1.03@C/N-TiO₂) were synthesized via solvothermal plus annealing approach, and their photocatalytic activities towards cyclohexane oxidation were investigated. It demonstrated that NiS_1.03@C/N-TiO₂-3 exhibited the highest cyclohexane conversion and product selectivity of 1.86% and 90% under visible light irradiation. Moreover, it had outstanding cycling stability, maintaining 86% of the original photocatalytic conversion rate after five cycles. On the one hand, such distinctly improved photocatalytic activities were ascribed to the enhanced visible light absorption induced by N-doping TiO₂. On the other hand, the p-n heterojunction and the built-in electric field could effectively facilitate the separation of electrons-holes. Besides, the presence of carbon would inhibit the agglomeration of NiS_1.03 particles, promoting the adsorption of cyclohexane and desorption of oxidation products, leading to further improvement of catalytic activity. To sum up, the enhanced visible light absorption, effective charge separation and the existence of carbon all contribute to the improvement of photocatalytic performance.