Coordination engineering in dual S-scheme heterojunction for photocatalytic applications: Research progress, key challenges and future horizons

The photocatalysis processes have been proven to be promising strategies for environmental remediation. Thus, it is of excellent research value to develop high-performance photocatalytic feedstocks with visible light response and stability. In this regard, heterojunction photocatalysts including type-I, -II, -III, Z-scheme, and S-scheme have shown great promise in various photocatalytic implementations. However, decreasing electron-hole recombination, ensuring light absorption, and enhancing redox abilities through the aforementioned photocatalysts have been regarded as some of the prime factors in the photocatalysis processes that remain challenging. Herein, as robust interfacial contact via three coordinated constituents, dual S-scheme heterojunctions for various photocatalytic implementations are reviewed. Initially, different heterojunction materials such as type-I, -II, -III, and Z-/S-scheme heterojunctions are discussed from recent reports. Then, in order to provide researchers and industrialists a better understanding of this novel class of heterojunction implementations in photocatalysis, a whole section has been devoted to examples of preparation and applications of dual S-scheme heterojunctions for photocatalytic wastewater remediation and bacteria photoinactivation. Benefits and  drawbacks in elaborating dual S-scheme heterojunction photocatalysts for the same purposes are addressed as well. This review attempts to encourage a rational design of dual S-scheme heterojunctions through three constituents coordination by choosing the adequate components to push the photocatalysis processes to their scalability barriers and unpractical applications.