The construction of p-n heterojunction for enhancing photocatalytic performance in environmental application: A review

Photocatalysis, a promising green technique, is drawing increasing attention in the field related to environmental protection, due to the advantages of low energy consumption, no pollution and easy operation. However, easy recombination of photogenerated electrons and holes makes apparent quantum yield low, which is a major limiting factor for the practical application of photocatalysis. Lately, a growing body of research shows that construction of p-n heterojunction may be an effective strategy to improve the photocatalytic performance. Normally, owing to the differences in Fermi levels and work functions between p-type and n-type semiconductors, the formation of p-n heterojunction can create an internal electric field, which will provide electrostatic force for regulating the charge transfer. In this review, the formation ways, combination types and effect mechanisms of p-n heterojunction based on staggered gap are summarized, and the charge transfer modes under the joint effects of built-in electric field and band structure are analyzed and discussed with emphasis. Meanwhile, the applications of p-n heterojunction in environment domain are also briefly summarized, including pollutant removal, sterilization, water splitting and CO2 reduction. The challenges and prospects for p-n heterojunction are also proposed. To sum up, current review may offer a valuable reference for designing and constructing p-n heterojunction in future work.