Photocatalytic Oxygen Evolution from Water Splitting

Photocatalytic water splitting has attracted a lot of attention in recent years, and O2 evolution is the decisive step owing to the complex four‐electrons reaction process. Though many studies have been conducted, it is necessary to systematically summarize and introduce the research on photocatalytic O2 evolution, and thus a systematic review is needed. First, the corresponding principles about O2 evolution and some urgently encountered issues based on the fundamentals of photocatalytic water splitting are introduced. Then, several types of classical water oxidation photocatalysts, including TiO2, BiVO4, WO3, α‐Fe2O3, and some newly developed ones, such as Sillén–Aurivillius perovskites, porphyrins, metal–organic frameworks, etc., are highlighted in detail, in terms of their crystal structures, synthetic approaches, and morphologies. Third, diverse strategies for O2 evolution activity improvement via enhancing photoabsorption and charge separation are presented, including the cocatalysts loading, heterojunction construction, doping and vacancy formation, and other strategies. Finally, the key challenges and future prospects with regard to photocatalytic O2 evolution are proposed. The purpose of this review is to provide a timely summary and guideline for the future research works for O2 evolution. Photocatalytic O2 evolution reaction is the rate‐determining step in the water splitting process. This review provides a comprehensive summary on the progress of photocatalytic O2 evolution from water splitting, involving the fundamentals and mechanism of O2 evolution, several typical photocatalysts in terms of their crystal structures, synthetic approaches and morphologies, and diverse strategies for O2 evolution activity improvement.