Cerium-modified BiPO₄ as a promising electrode material for hybrid supercapacitors

In this research work, the electrochemical response of BiPO₄ was optimized by varying the Ce concentration to 1, 2, and 3%. The XRD analysis confirmed the monoclinic structure of the prepared BiPO₄ nanoparticles with space group P21/a and P21/m. EDX studies indicated the presence of Ce with different concentrations in the doped BiPO₄. The electrochemical investigations showed that Ce (3%)-doped BiPO₄ exhibited the best electrochemical properties with a 784.2 F/g of specific capacitance at a scan rate of 5 mV/s. The charge storage nature presented hybrid behavior of the electrode material with b = 0.7, with 74% capacitive and 26% diffusive contributions. The prototype device based on a two-electrode setup presented a maximum energy density of 24.11 Wh/kg at 1 A/g and 4900 W/kg of power density at 7 A/g, with a 79.43% capacity retention for 1000 GCD cycles. The XPS analysis revealed the occurrence of multiple oxidation states of Ce (Ce³⁺ and Ce⁴⁺) and Bi (Bi³⁺ and Bi⁵⁺), responsible for enhanced electrochemical response of Ce-doped BiPO₄ nanomaterials for hybrid supercapacitors. The 3% cerium-doped BiPO₄ showed enhanced conductivity and facilitated electrochemical redox reactions, indicating its potential for energy storage applications.