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 Co 9 S 8 nanoflower/RP nanosheet heterojunction was fabricated using a solvothermal solvent evaporation strategy for effectively enhancing the photocatalytic H 2 evolution. The investigation shows that the introduction of spherical Co 9 S 8 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 H 2 evolution overpotential, leading to a H 2 evolution rate of 1562.5 μmol·h –1 ·g –1 over 1% Co 9 S 8 /RP sample, which is 8.2 and 18.9 times that of pure RP and Co 9 S 8, respectively. In addition, the water contact angle of RP is obviously reduced from 11.8° to 3.1° after introducing Co 9 S 8; this superhydrophilic surface is conducive to the adsorption of water molecules on the catalyst surface. Further investigation shows that Co 9 S 8 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 Co 9 S 8 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 H 2 evolution.