Electrolyte-driven modulation of charge storage mechanisms in Co metal-organic frameworks for advanced...

This study examines the influence of electrolytes and the molarity-dependent electrochemical evaluation of Co-MOF-based electrodes for supercapacitor applications. The synthesized Co-MOF was analyzed using XRD, FTIR and FE-SEM techniques, which collectively confirmed the successful formation of the material. The electrochemical performance was evaluated using CV, GCD and EIS in alkaline electrolytes of different molarities. Co-MOF exhibited a C _sp of 379.31 F g^-1 and 852.5 F g^-1 in KOH and NaOH, respectively, at a scan rate of 2 mV s^-1, indicating superior response in NaOH. Similarly, GCD measurements revealed an enhanced C _sp of 1147.2 F g^-1 at 0.5 A g^-1 in NaOH, compared with 317.86 F g^-1 in KOH. The molarity of the electrolyte was varied (1 M NaOH, 3 M NaOH and 5 M NaOH), and 1 M NaOH displayed optimal performance, while maintaining a ∼98% of the capacitance retention after 10 000 cycles. A symmetric Co-MOF Swagelok supercapacitor utilizing 1 M NaOH showed a C _sp of 37.7 F g^-1 (CV) and 14.9 F g^-1 (GCD) at 0.25 A g^-1 with a maximum E _d of 3.73 W h kg^-1 at a P _d of 118.75 W kg^-1 and ∼43.96% retention after 10 000 cycles. Similarly, at a scan rate of 2 mV s^-1, the Co-MOF pouch cell exhibited a C _sp value of 21.42 F g^-1 from CV and a peak capacitance of 1.68 F g^-1 when evaluated at 0.25 A g^-1 for GCD. Ragone analysis revealed that the device delivered an E _d of 0.22 W h kg^-1 at a corresponding P _d measured at 43.75 W kg^-1. The results underscore the importance of concentration and electrolyte selection as critical parameters for Co-MOF supercapacitor performance.