Efficient design of mesoporous NiS/FePO4 S-scheme heterojunction photocatalyst for efficiently enhancing hydrogen evolution under visible light

Abstract

Heterogeneous photocatalysis has been touted as an impressive technique thanks to its provision of a clean, economical, and sustainable approach for generating “green” hydrogen for mitigating greenhouse gas emissions. The rapidly occurring recombination of photo-induced charge pairs is touted as an important roadblock to photocatalytic hydrogen production. The present research presents the controlled building of innovative mesoporous NiS/FePO₄ (NiS/FPO) heterojunction photocatalysts, incorporating varying NiS concentrations via a modified sol-gel and wet impregnation technique, aimed at promoting light-triggered hydrogen generation from a glycerol aqueous solution, with an in situ loaded Pt (co-catalyst) on the surface of the photocatalyst during the photocatalytic experiments. The highest-performance photocatalyst, 9 % NiS/FPO, possessed a mesoporous two-dimensional (2D) architecture, a large surface area (115 m²/g), a wider absorption boundary (483.87 nm), and considerable efficacy in separating photo-induced electron/hole (e⁻/h⁺) pairs, together with substantial redox capabilities. Consequently, the 9 % NiS/FPO at an optimal concentration of 2.0 g/L achieved a better hydrogen yield of 33.60 mmol g⁻¹, with a maximized rate of 4.252 mmol h⁻¹ g⁻¹, eclipsing the rate obtained utilizing the pristine FPO by roughly 141.7 occasions. The five-run investigations demonstrated the notable stability of the 9 % NiS/FPO heterojunction. The primary cause of this astounding efficacy is the design of the S-scheme heterojunction photocatalyst, which strengthened the separation of photo-induced carriers, augmented the capacity to harvest and harness visible light, and heightened redox capabilities. The current study introduces an innovative and pragmatic approach to developing superior S-scheme heterojunction photocatalysts for the efficient and reliable production of hydrogen from water.