Photocatalytic Oxygen Evolution from Water Splitting.

Photocatalytic water splitting has attracted a lot of attention in recent years, and O 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 O evolution, and thus a systematic review is needed. First, the corresponding principles about O 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 TiO, BiVO, WO, -FeO, 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 O 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 O evolution are proposed. The purpose of this review is to provide a timely summary and guideline for the future research works for O evolution.