Binder-free phosphor-coated multiphase bismuth cobalt-selenide electrode for solar-charged quasi-solid-state hybrid supercapacitors

The enormous utilization of fossil fuels and the accelerated progression of global warming have irreversible destructive consequences on Earth's biodiversity. In response to this concern, there is a growing need to adopt green and renewable energy sources as effective strategies for mitigating environmental challenges. Herein, we report the novel synthesis and electrochemical properties of a binder-free phosphorus-coated multiphase bismuth-cobalt selenide/nickel foam (P@BCS/NF) electrode. Phosphorization was performed under an N₂ atmosphere in a tube furnace to cover the electrodes. The synthesized electrode exhibited a porous nanorod morphology, which enhanced its electrochemical and energy storage properties. The P@BCS/NF electrode delivered a high areal capacity value of 836.4 µAh cm⁻² in 1 M KOH electrolytic solution with excellent cycling stability, 81.4 % capacity retention, and 98.8 % coulombic efficiency over 10,000 cycles. A quasi-solid-state hybrid supercapacitor (QHSC) device was constructed using P@BCS/NF as the positive electrode and activated carbon as the negative electrode. The QHSC device showed maximum areal energy and power density values of 384.37 μWh cm⁻² and 21750 μW cm⁻², respectively, together with high stability of 94.4 % capacitance retention after 10,000 cycles. The practical application of the QHSC device was demonstrated in a PVA-KOH electrolytic environment by powering various electronic devices.