Current Trends and Future Perspectives on ZnO-Based Materials for Robust and Stable Solar Fuel (H2) Generation

Abstract

Zinc oxide (ZnO) has been utilized for photocatalytic water splitting due to its excellent performance, low cost, non-toxicity, thermal stability, and chemical stability. However, despite these remarkable properties, ZnO has significant drawbacks, such as photocorrosion and an inability to utilize visible light due to its wide band gap of 3.3-3.4 eV. Structurally, ZnO exists in three different forms: rocksalt, cubic blende, and hexagonal wurtzite. It has been reported that the wurtzite structure produces more H₂ compared to its counterparts. Herein, we discuss several techniques for synthesizing zinc oxide and how incorporating zinc oxide nanoparticles with metal oxides, sulfides, and other materials can enhance its performance in the visible light region. Recently, integrating ZnO with TiO₂ –Ag using an S-scheme heterostructure boosted the H₂ activity rate to approximately 60.0 mmol/g/h, which is about 166 times superior to pristine ZnO. This improvement is attributed to the enhanced light absorption and charge transfer facilitated by Ag doping. This review examines ZnO-based photocatalytic H₂ generation via water splitting with different modification strategies and explores future outlooks for improving performance of ZnO.