Insulator in photocatalysis: Essential roles and activation strategies

Developing novel photocatalysts with high efficiency will inject expectation into the field of photocatalysis towards the realization of practical applications. In recent years, the insulator-based photocatalysts have ignited the enthusiasm of research community owing to their abundant, cost-effective and eco-friendly features. However, there are few comprehensive summaries refer to the rational engineering and the function mechanisms of insulator-based photocatalysts so far. In this mini review, we present an overview of the progress for insulatorrelated photocatalysts and explore the exciting potential of insulating materials. First, we highlight the roles of insulator in photocatalysis, which include (1) acting as co-catalyst to facilitate the migration of charge carriers from the semiconductor photocatalyst, (2) acting as robust support to disperse the semiconductor photocatalyst and/or improve the adsorption of substrate, and (3) acting as barrier layer to prevent the recombination of charge carriers and/or photo-corrosion. Then, strategyies to activate the insulator by modulating the surface property to stimulate the separation of charge carriers and improve the light absorption are summarized, which include (1) introduction of oxygen vacancies, (2) introduction of metal-defects and (3) utilization of localized surface plasma resonances (LSPR) effect. Finally, the prospects and challenges for the development of efficient insulator photocatalysts are discussed.