Bridge engineering in photocatalysis and photoelectrocatalysis.

Solar driven photocatalysis and photoelectrocatalysis have emerged as promising strategies for clean, low-cost, and environmental-friendly production of renewable energy and removal of pollutants. There are three crucial steps for the photocatalytic and photoelectrochemical (PEC) processes: light absorption, charge separation and transportation, and surface catalytic reactions. While significant achievement has been made in developing multiple-component photocatalysts to optimize the three steps for improved solar-to-chemical energy conversion efficiency, it remains challenging when weak interfacial contact between components/particles hinders charge transfer, restricts electron-hole separation and lowers the structural stability of catalysts. Moreover, owing to the mismatch of energy bands, an undesirable charge transfer direction leads to an adverse consequence. To tackle these challenges, bridges are implemented to smoothen the interfacial charge transfer, improve the stability of catalysts, mediate the charge transfer directions and improve the photocatalytic/PEC performance. In this review, we present the advances in bridge engineering in photocatalytic/PEC systems. Starting with the definition and classifications of bridges, we summarize the architectures of the reported bridged photocatalysts. Then we systematically discuss the insight into the roles and fundamental mechanisms of bridges in various photocatalytic/PEC systems and their contributions to activity enhancement in various reactions. Finally, the challenges and perspectives of bridged photocatalysts are featured.