Design and applications of hollow-structured nanomaterials for photocatalytic H2 evolution and CO2 reduction

Photocatalysis is considered a prospective way to alleviate the energy crisis and environmental pollution. It is therefore extremely important to design highly efficient photocatalysts for catalytic systems. In recent years, hollow-structured materials have attracted considerable interest for application in energy conversion fields owing to their large specific surface areas, improved light absorption, and shortened charge carrier transfer path. Because they contain inner and outer surfaces, hollow-structured materials can provide a superior platform for the deposition of other components. A number of hollow-structured hierarchical systems have been designed and fabricated in recent decades. It is important to rationally design and construct complex hierarchical structures. In this review, general preparation approaches for hollow-structured materials are presented, followed by a summary of the recent synthesis methods and mechanisms of typical hollow-structured materials for applications in the photocatalytic field. Complex hollow-structured hierarchical photocatalysts are classified into two types, hollow cocatalyst-based and hollow host photocatalyst-based, and the design principle and analysis of the photocatalytic reaction mechanism for photocatalytic H2 evolution and CO2 reduction are also introduced. The effects of hollow-structured materials have also been investigated. This review provides a reference for the rational construction of advanced, highly efficient photocatalytic materials.