Fabrication and performance evaluation of the NPC/amorphous-Sn2P2O7 by dealloying of CuNiSnP alloy for supercapacitor application

Present study focuses on the evaluation of the energy storage performance of possible pyrophosphate supercapacitor materials obtained by dealloying process. The electrochemical behavior was investigated by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS) techniques using a system based on three-electrode cell in 1 M KOH electrolyte solution. A direct assessment of the influence of dealloying time for capacitance was performed, showing that partial dealloying improves energy storage. Furthermore, the synthesized materials were investigated morpho-structurally to present behavior of the materials at immersion times between 3 and 24 h. Obtained results presents that the highest capacitance value about 269.36 mF cm⁻² measured from CV analysis was observed for the electrode at 3 h immersion time at 5 mV s⁻¹ scan rate. The GCD results confirmed also the superiority of the electrode material by recording the maximum specific capacitance of 268.7 mF cm⁻² at 1 mA cm⁻² calculated for the electrode at 3 h immersion time. All the as-synthesized electrodes presented an excellent cyclic stability showing an increase in retention rates over 100 %. For the as-obtained electrode a retention rate about 129.33 % at 24 h immersion time over 500 cycles, was obtained. In addition, aqueous symmetric supercapacitors were assembled based on the experimental program. Capacitance values were calculated from the CV data as a function of potential window and scan rate. The highest capacitance was observed for the CSP-12 h//CSP-12 h symmetric supercapacitor, reaching 49.24 mF cm⁻² at 1.4 V. As a function of scan rate, the CSP-24 h//CSP-24 h device exhibited the highest capacitance, reaching 45.72 mF cm⁻² at 5 mV s⁻¹. GCD measurements as a function of potential window showed that the CSP-6 h//CSP-6 h and CSP-12 h//CSP-12 h devices demonstrated the best performance, with the highest capacitance values of approximately 46 mF cm⁻² achieved at 1.4 V. Furthermore, the CSP-12 h//CSP-12 h device delivered a power density of 5.46 mW cm⁻² at an energy density of 0.027 mWh cm⁻². Over 3000 cycles, the maximum retention rate was approximately 30.42 %, observed for the CSP-3 h//CSP-3 h device. This research presents a promising technique for producing pyrophosphate material for supercapacitor application.