The solar-driven photocatalytic process has been evolved as a promising technology for both hexavalent chromium reduction and organic pollutants oxidation. Although both reactions are based on the same principle of photoinduced interfacial charge transfer, different catalysts and reaction conditions are required in two processes. This review revealed the scientific advances in dual-functional photocatalytic processes that enable simultaneous hexavalent chromium reduction and organics oxidation. Firstly, the basic principles of dual-functional photocatalysis are briefly discussed whereby the key concept of the system is the simultaneous oxidation of organic pollutants via photogenerated holes and reduction of hexavalent chromium via photogenerated electrons. Then, advances in dual-functional photocatalysis for the simultaneous removal of hexavalent chromium and organics are presented and discussed in terms of catalysts classification, including TiO₂-based, bismuth-based and g-C₃N₄-based catalysts. Finally, the prospects, challenges and new perspectives of feasible solutions for dual-functional photocatalytic catalysts design are presented. Overall, this paper provides new insights on the modulation strategies and conformational relationships of dual-functional materials for researchers in the field of photocatalysis, which is beneficial for the practical applications of dual-functional materials in environmental remediation.

Faced with the growing consumption of fossil fuels and the consequent energy/ecological crisis, photocatalysis has become a realistic option to develop new energy source and realize the carbon neutrality. Heterojunction photocatalysts constructed by multiple semiconductors with staggered band structure can spatially separate redox reaction sites to realize synergistic oxidation and reduction reactions, and have captured broad interest. However, the undesigned heterojunctions still encounter some headache difficulties, that is the poor interfacial contact, which will block carrier mobility, thus result in inefficient and instable catalysts. Recently, researchers have been focusing on constructing chemical bonds (especially covalent bonding) between different semiconductors to induce the formation of intimate and stable interface contact. Herein, this review article presents the state-of-the-art progress on interfacial chemical bonds (ICB) in heterojunction photocatalysts and clarifies the function mechanism for enhancing photocatalysis. Given that the formation of ICB strongly depends on the surface characteristics of semiconductors, we clarify the formation mechanism and put forward rational design strategies. More importantly, the current photocatalytic applications of ICB are reviewed to have a deep understanding of structure–activity related mechanisms. Finally, our brief outlooks on the current challenges and future development trends of ICB for next-generation photocatalysts are pointed out to create brand-new strategies for optimizing photocatalytic properties and accelerate the practical applications of ICB with high-performance.

Oxygen evolution reaction (OER) still suffers from the bottleneck in electrocatalytic water splitting. Herein, in virtue of volcano plots drawn by theoretical calculation, the (001) facet was screened as the superb facet of orthorhombic CoSe₂ for OER. Afterwards, CoSe₂(001) nanosheets were synthesized and the exposure ratio of (001) facet is controllable with thermodynamics methods effectively. The single-facet CoSe₂(001) delivered an overpotential as low as 240 mV at 10 mA·cm⁻² in 1 M KOH, which outperformed the bulk (380 mV) as well as other CoSe₂-base OER catalysts reported before. Especially, a shorter Co–Co path was observed in CoSe₂(001) by X­ray absorption spectroscopy. Further density functional theory (DFT) studies revealed that the reversible compression on the shorter Co–Co path could regulate the electronic structure of active sites during the OER process, and thus the energy barrier of the rate-determining step was reduced by 0.15 eV. This work could inspire more insights on the modification of electronic structure for OER electrocatalysts.