Rational design of yolk–shell nanostructures for photocatalysis

Photocatalysis is a promising route to convert solar energy into chemical energy directly, providing an alternative solution to environment and natural resource problems. Theoretically, all photocatalytic reactions are driven by charge carriers whose behavior can be divided into charge generation, separation, migration and surface reactions. Efficiencies of charge utilization in every step determine the overall performance of photocatalysis. Yolk-shell (YS) structures can provide an ideal platform for the efficient utilization of charge carriers. Typically, a YS structure is constructed from a hollow shell and an inner core, which can enhance light scattering in the hollow space and provide a large surface to create sufficient active sites, both of which can significantly improve the efficacy of charge utilization. Additionally, many strategies can be adopted to modify the YS structure for further enhancement of charge behaviors in every step. Existing reviews about YS structures mainly concentrate on the universality of the application of YSs, while the strategies to improve photocatalytic performance based on YSs have not been elaborately illustrated. This review describes the classification, synthesis, formation mechanism of YS structures and the rational regulation of the behaviors of photogenerated charge carriers, aiming at their effective utilization based on YS structures in heterogeneous photocatalytic reactions.