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

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, NiSpg-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. NiSpg-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 Wcm(-2)), the aqueous dispersion of NiSpg-C3N4 exhibits a temperature elevation of 56.7 degrees 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 H-2 production rate, with the value 31.3 mmol.g(-1).h(-1). In five cycles of reactions for 30 h, the H-2 production rate remains constant. The synergy between sulfur vacancy and photothermal effect of NiS play significant roles in the enhancement of H-2 production property.