Heterojunction Systems for Photocatalysis

Over the last decades, the ever-increasing energy and environmental problems, mainly arising from the consumption of fossil energies, have urged the development of green and sustainable technologies for sufficing the energy demand by mankind. Among various proposed technologies, photocatalysis for conversion of the sunlight to chemical energy has aroused worldwide attention. However, up to date, the photoconversion efficiency via photocatalysis remains unsatisfactory mainly due to the rapid charge carrier recombination. Lately, heterojunction photocatalysts have emerged as an efficient photocatalytic system for ameliorating the photocatalytic activity because of their capability in improving charge carrier utilization efficiency. The maturity of such photocatalytic systems could provide enormous opportunities for achieving practical photocatalytic applications. In this chapter, general concepts of various heterojunction photocatalysts including type-II heterojunction, p–n junction, surface junction, direct Z-scheme, and step-scheme (S-scheme) heterojunction photocatalysts are outlined. Then, the characterization methods and applications for these heterojunction photocatalysts are summarized. Finally, the future outlook for the heterojunction photocatalysts is presented.