A perspective on NiCo2O4-based photocatalysts: from fundamentals, modification strategies to applications

Semiconductor-mediated photocatalysis holds promise in both clean energy supply and environmental remediation, and is regarded as one of the most ideal approaches to achieving carbon neutrality in the future. Low-cost, visible-light-response, and high-efficiency semiconductor photocatalysts are key to the practical application of photocatalysis. Compared with the binary counterpart Co₃O₄, ternary NiCo₂O₄ has high cation disorder, variable electronic structure, and asymmetry dual metal sites, thus exhibiting great potential in developing high-efficiency visible-light-response photocatalysts. In this review, the fundamental advantages and drawbacks of NiCo₂O₄ for heterogenous photocatalysis are first introduced in terms of the crystal structure, electronic band structure, and surface atom exposure. Modification strategies for NiCo₂O₄-based photocatalysts are then surveyed and commented on in detail, including the aspects of morphology regulation, defect engineering, construction of heterojunctions, loading cocatalysts, and integration of multiple strategies. Furthermore, the research progress of NiCo₂O₄-based photocatalysts for water splitting, carbon dioxide reduction, and pollution degradation is summarized. In particular, some research gaps and problems with property modifications and practical applications are also highlighted in this context, which offers specific directions for future research. Finally, this review is concluded by outlining the challenges and opportunities of NiCo₂O₄-based photocatalysts for solar energy conversion.