Recent advances in photoelectrochemical potential improvement of CuBi2O4: Energy applications

• CuBi 2 O 4 is an effective photocatalyst for energy production and storage. • CuBi 2 O 4 is used in photoelectrochemical applications for H 2 evolution, CO 2 reduction, solar cells, batteries, etc. • CuBi 2 O 4 can be prepared by using various synthesis routes like the hydrothermal method, sol gel method, etc. • CuBi 2 O 4 can be interlinked with various other materials for synthesizing heterojunctions to enhance its performance. CuBi 2 O 4 , 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 (TiO 2 ) is a widely used photocatalyst that absorbs UV light, CuBi 2 O 4 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. CuBi 2 O 4 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 CuBi 2 O 4 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. CuBi 2 O 4 also forms heterojunctions with perovskites and photocatalysts (such as SrTiO 3 , TiO 2 , ZnO etc.), which enhance its photocurrent density and photostability, but it is quite challenging. Hence, this review highlights the CuBi 2 O 4 -based materials, with their synthesis methods and applications in the photoelectrochemical H 2 O splitting for H 2 generation, CO 2 reduction, solar cells, and batteries that describe their importance in producing energy.