Surface Oxygen Vacancy Engineering for Enhanced Volatile Organic Compounds Removal in Solar-Interfacial Water Evaporation

Solar-interfacial water-vapor conversion has emerged as a promising method for clean water production, particularly in water-scarce regions, but a major challenge is the volatile organic compounds (VOCs) along with water vapor, leading to polluted condensed water. This study introduces a novel design strategy that leverages surface oxygen vacancies (OVs) in photocatalysts to maximize both oxygen (O 2 ) utilization from the air and photocarrier efficiency at the air–water interface, building upon previous research that demonstrated that oxygen concentration at the interface can be significantly higher than that in bulk water. By enhancing oxygen adsorption and facilitating charge carrier separation, OVs significantly improve reactive oxygen species (ROS, including ·O 2 – and ·OH) generation and overall photocatalytic activity. As a demonstration, the surface OVs-engineered BiOCl-based photocatalytic solar interfacial evaporator demonstrated a 3.41-fold increase in VOC (phenol) removal efficiency compared to a conventional system, achieving over 99.6% VOC removal in condensed water and maintaining a high water vapor generation flux of 1.90 kg/m 2 /h. This innovative design was further validated using ZnO-based photocatalysts, demonstrating the broad applicability of OV-engineering in interfacial systems. By fully utilizing both the high oxygen content at the air–water interface and improving photocarrier dynamics, this approach represents a significant advancement in photocatalytic water treatment technologies, offering a scalable and highly efficient solution for VOC removal and clean water production.