A promising supercapacitor electrode material of CuBi2O4 hierarchical microspheres synthesized via a coprecipitation route

• CuBi2O4 hierarchical microspheres are synthesized via a coprecipitation method.
• The electrochemical performances of the as-prepared samples are investigated.
• The sample composed of 0.5–1 μm microspheres exhibits the highest specific capacity.
• The specific capacity value is larger than that for most transition metal oxides.

CuBi2O4 hierarchical microspheres are synthesized via a coprecipitation method, where the effect of the NaOH concentration in precursor solution on the product morphology is investigated. At n(NaOH) = 1 M, irregular microspheres of 0.5–1 μm are produced. With increase in the concentration of NaOH, the microspheres grow bigger in size and more regular in morphology. When the NaOH concentration is increased up to 6 M, regular microspheres of 4–6 μm in diameter are obtained. These microspheres are constructed from nanorods with 30–60 nm in diameter and 200–400 nm in length via the hierarchical self-assembly process. The electrochemical performances of the as-prepared samples are investigated by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge-discharge. It is demonstrated that the sample composed of 0.5–1 μm microspheres exhibits the highest specific capacity, reaching about 1895 F g−1 in a 2 M KOH electrolyte at a measured current density of 1 A g−1. This value is larger than the specific capacity for most transition metal oxides. Due to its excellent electrochemical performance, CuBi2O4 could find a promising application as the supercapacitor electrode material.