Coordination Polymer Derived NiS@g-C₃N₄ Composite Photocatalyst for Sulfur Vacancy and Photothermal Effect Synergistic Enhanced H₂ Production

Abstract

To obtain the photocatalyst composed by sulfur vacancies rich NiS and graphitic carbon nitride (g-C3N4), a simple method has been found for using coordination polymer as precursor. Based on this strategy, an effective composite photocatalyst, NiS@g-C3N4, is synthesized successfully through the calcination of a Ni2+ based coordination polymer with 2-mercapto-5-propylpyrimidine as ligand. In this photocatalyst, the NiS nanoparticles with small size disperse evenly in 2-mercapto-5-propylpyrimidine derived g-C3N4. Electron paramagnetic resonance (EPR) suggests there are a lot of sulfur vacancies in NiS@g-C3N4. NiS@g-C3N4 exhibits intensive adsorption in the near-infrared region, which endows NiS@g-C3N4 with promising photothermal effect. With a 980 nm laser as light source (0.44 W·cm–2), the aqueous dispersion of NiS@g-C3N4 exhibits a temperature elevation of 56.7 °C with photothermal conversion efficiency of 58.2%. Under irradiation of simulated solar light, without Pt co-catalyst, NiS@g-C3N4 possesses a promising photocatalytic H2 production rate, with the value 31.3 mmol·g–1·h–1. In five cycles of reactions for 30 h, the H2 production rate remains constant. The synergy between sulfur vacancy and photothermal effect of NiS play significant roles in the enhancement of H2 production property.