S-Scheme CdS/CuWO <sub>4</sub> Heterojunction Optimizes Reaction Kinetics for Enhanced Photocatalytic H <sub>2</sub> Evolution
Shuang Ma, Wenke Wang, Zhenze Hu, Shukui Shi, Peiying Yang, Yanmin Hou, Hailong Zhang, Changdong Chen, Z. F. Wang, Haopeng Jiang
Abstract
In the field of photocatalytic water splitting for hydrogen (H 2 ) production, heterojunction engineering is regarded as one of the effective strategies to enhance the separation efficiency of photogenerated charge carriers and the redox capability. In this work, a simple electrostatic self-assembly method was employed to intimately couple CuWO 4 nanoparticles with CdS nanorods, thereby constructing a CdS/CuWO 4 heterojunction for photocatalytic H 2 evolution from water. In situ XPS and surface photovoltage measurements confirm the presence of a strong built-in electric field (IEF) and an S-scheme charge transfer pathway at the CdS/CuWO 4 heterojunction interface. Meanwhile, the IEF strength in the CdS/CuWO 4 heterojunction is 2.16 and 5.23 times that of CdS and CuWO 4, respectively. Furthermore, DFT calculations reveal that the H* adsorption energy on the CdS/CuWO 4 heterojunction is −0.19 eV, compared with −0.57 eV on CdS, indicating that constructing an S-scheme heterojunction can optimally tune the reaction kinetics of photocatalytic H 2 evolution and thereby enhance the H 2 production activity. Using lactic acid as a sacrificial agent, the optimized CdS/CuWO 4 S-scheme heterojunction exhibits a higher H 2 evolution rate of 54.53 mmol·g –1 ·h –1, which is approximately 3.86 times that of CdS nanorods (14.1 mmol·g –1 ·h –1 ). Continuous photocatalytic H 2 evolution tests demonstrate that the CdS/CuWO 4 heterojunction maintains excellent photostability after 12 h of uninterrupted illumination. This study provides insights into the design and development of efficient S-scheme heterojunctions to further improve the activity and stability of photocatalytic H 2 production.