S-Scheme Co9S8 Nanoflower/Red Phosphorus Nanosheet Heterojunctions for Enhanced Photocatalytic H2 Evolution

Environmental and energy problems can be effectively alleviated by solar photocatalysis technology. In this work, an S-scheme Co9S8 nanoflower/RP nanosheet heterojunction was fabricated using a solvothermal solvent evaporation strategy for effectively enhancing the photocatalytic H2 evolution. The investigation shows that the introduction of spherical Co9S8 can not only increase the electrochemical active surface area, provide more photoinduced charges, and decrease the electrochemical impedance of the composite system but also reduce the H2 evolution overpotential, leading to a H2 evolution rate of 1562.5 μmol·h–1·g–1 over 1% Co9S8/RP sample, which is 8.2 and 18.9 times that of pure RP and Co9S8, respectively. In addition, the water contact angle of RP is obviously reduced from 11.8° to 3.1° after introducing Co9S8; this superhydrophilic surface is conducive to the adsorption of water molecules on the catalyst surface. Further investigation shows that Co9S8 and RP can form a built-in electric field, which can accelerate the migration of photoexcited carriers from the conduction band of RP to the valence band of Co9S8 along the S-scheme path and reserve the highly active charges. This work provides an effective strategy to design a low-cost, extremely active, and stable RP-based S-scheme heterojunction for photocatalytic H2 evolution.