S-Scheme Co<sub>9</sub>S<sub>8</sub> Nanoflower/Red Phosphorus Nanosheet Heterojunctions for Enhanced Photocatalytic H<sub>2</sub> Evolution
Fangli Zhao, Meiling Zhang, Dan Yan, Xiaoyun Hu, Jun Fan, Tao Sun, Enzhou Liu
Abstract
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.