N-doped carbon layer promoted charge separation/transfer in WP/g-C3N4 heterostructures for efficient H-2 evolution and 4-nitrophenol removal

Monodispersed WP nanoparticles were encapsulated in nitrogen-doped carbon (NC) layers via thermal polymerization at high temperature. The intimate interface between WP and NC accelerated charge transfer and elevated the electroconductivity. As-prepared WP@NC nanocomposites revealed enhanced electrocatalytic hydrogen evolution reaction (HER) activities in both of acidic and alkaline electrolytes with Tafel slopes of 73 and 85 mv/dec, respectively. Furthermore, WP@NC nanocomposites instead of noble metal co-catalysts were loaded on superior thin g-C3N4 nanosheets (CN) by thermal polymerization at different temperature. In the case of without Pt, the photocatalytic hydrogen generation rate of CN/WP@NC heterojunctions prepared using optimized conditions reached 1217.6 mu mol g(-1) h(-1), which was similar to 196 folds of pure g-C3N4 nanosheets. This is ascribed to that N-doped carbon layers on WP improved the separation and transfer efficiency of photogenerated charge carriers. Interestingly, the carbon layers improved the chemical stability and corrosion resistance to ensure enhanced photocatalytic hydrogen generation in simulated seawater. In addition, the sample revealed outstanding light-assisted elimination capability of 4-nitrophenol (4-NP) because of the selective hydrogenation reaction to 4-aminophenol and photodegradation reaction of 4-NP. Under visible light irradiation, the removal efficiency using CN/WP@NC reached 99% within 10 min. The kinetic constant (0.443 min(-1)) was 17.8 times of that of g-C3N4 nanosheets. This work supplied an efficient method to fabricate bi-functional noble-metal-free catalyst towards clean energy production and environment remediation.