Recent advances in photoelectrochemical potential improvement of CuBi2O4: Energy applications

CuBi₂O₄, or copper bismuth oxide, is the most important spinel oxide and a promising material that shows its excellent potential in photocatalytic applications. As titanium dioxide (TiO₂) is a widely used photocatalyst that absorbs UV light, CuBi₂O₄ absorbs visible light too because of its narrower band gap energy (1.5–1.8) eV, and this makes it much efficient in various applications, as UV light is not widespread. CuBi₂O₄ is also used as a photoelectrode material for photoelectrochemical (PEC) cells. In addition to photocatalysis, it is specifically used as an electrode material in batteries as its structural stability and good capacity make it suitable for effective charge storage and long-term cycling. Recent advances in the synthesis of CuBi₂O₄ from the hydrothermal method, sol–gel method, co-precipitation, etc., have enhanced its production with improved surface areas and engineered morphologies, hence improving its performance in storing energy. CuBi₂O₄ also forms heterojunctions with perovskites and photocatalysts (such as SrTiO₃, TiO₂, ZnO etc.), which enhance its photocurrent density and photostability, but it is quite challenging. Hence, this review highlights the CuBi₂O₄-based materials, with their synthesis methods and applications in the photoelectrochemical H₂O splitting for H₂ generation, CO₂ reduction, solar cells, and batteries that describe their importance in producing energy.