Solid mediator Z-scheme heterojunction photocatalysis for pollutant oxidation in water: Principles and synthesis perspectives

Background: The solid mediator Z-scheme heterojunctions are promising photocatalysts that have narrow band gaps to allow excitation of incorporated electrons under visible lights but with sufficient separation of the yielded electron hole-pairs and without suffering the reduction of their oxidization and reduction powers. Successful synthesis of mediator Z-scheme heterojunction acquires production of constituent semiconductors with desired Fermi levels and close contacts of the semiconductors with sandwiched metal mediator. 
Methods: This mini-review discussed briefly the principles of photocatalyst and heterojunction photocatalysts, and then the current research and development studies on the way to design and synthesis of Z-scheme heterojunction were summarized. 
Significant findings: Based on literature results, the perspectives to design and synthesis of a solid mediator Z-scheme for degrading specific pollutant were discussed and outlined. An illustrative example of design and synthesis of a novel Z-scheme photocatalyst, CuFe₂O₄/Cu/UiO66-NH₂, with demonstration of its photodegradation performance of dye rhodamine 6 G, was presented at the end of the review.