Heterojunction catalyst in electrocatalytic water splitting

In a water electrolysis system, the cathode and anode produce H2 and O2 with HER and OER, respectively. The energy conversion efficiency of the electrolysis systems is about 56–73% in practical application, and the low energy conversion efficiency greatly limits the large-scale application. Hence, the electrocatalytic water splitting has attracted much attention. Recently, a variety of heterogeneous catalysts have emerged, showing high catalytic water splitting performance. Among them, the heterojunction catalysts occupied a very important position in emerging catalysts. In the heterojunction catalysts, electrons can be rearranged on heterostructures interfaces to modify the properties of active sites, and synergy of different active sites is used to promote the reaction kinetics. The heterojunction catalysts often show a better activity of electrolysis water than single-component catalysts. Herein, we mainly summarize the design strategies and synthesis methods of various heterojunction catalysts and the related applications of these heterojunction catalysts in HER and OER, and further discusses the catalytical mechanisms in HER and OER processes respectively. Through the summary of present progress in electrocatalytic water splitting, this review provides a reasonable prospect on heterojunction catalysts in electrocatalytic water splitting.