The Capacitive Property Enhancement of CoFeP-Ni(OH)2/Nickel Foam Electrodes via an Interfacial Integration Strategy for Asymmetric Supercapacitors

We report the fabrication of CoFeP-Ni(OH)₂/nickel foam (NF) composite electrodes via a two-step strategy involving the hydrothermal synthesis of Ni(OH)₂ on nickel foam followed by the electrochemical deposition of CoFeP. The integration of the Ni(OH)₂ interlayer not only provides a structurally robust interface but also facilitates synergistic redox activity, thereby significantly boosting the pseudocapacitive behavior of the electrode. Comparative analysis with bare CoFeP/NF reveals that the presence of the Ni(OH)₂ layer contributes to enhanced charge transfer efficiency and an increased electroactive surface area. Among the samples prepared under varying deposition cycles, the optimized CoFeP-Ni(OH)₂/NF electrode exhibits a high areal capacitance of 4244 mF cm^-2 at 2 mA cm^-2. Furthermore, an asymmetric supercapacitor device assembled with CoFeP-Ni(OH)₂/NF as the positive electrode and activated carbon as the negative electrode delivers a maximum energy density of 0.19 mWh cm^-2 at a power density of 0.37 mW cm^-2 and excellent cycling stability, retaining 72% of its initial capacitance after 5000 cycles at a high current density of 8 mA cm^-2.