Bifunctional CoSn(OH)6/MnO2 composite for solid-state asymmetric high power density supercapacitor and for an enhanced OER

Bifunctional composite made of CoSn(OH)6 with MnO2 has been developed to explore the synergistic effects in specific capacitance measurement and in oxygen evolution reaction activity. The bifunctional composite was prepared by perovskite structured hydroxide such as CoSn(OH)6 composited with different phases of metal oxides such as MnO2 or as mixed phase of Mn2O3–Mn3O4 (MP-MnO). The morphological and surface properties of CoSn(OH)6/MP-MnO and CoSn(OH)6/MnO2 composites were studied by SEM, HR-TEM, XRD, TG/DTA, BET and XPS techniques. In comparison, CoSn(OH)6/MnO2 composite exhibits high specific capacitance (Csp) of 1472 Fg-1 at 1 Ag-1 current density in three electrode configuration with good capacitance retention of 95.3% after 5000 cycles. In addition, the composite shows high Csp of 38.2 Fg-1 at 0.25 Ag-1 current density in two electrode configuration. Further, an assembled asymmetric supercapacitor device (AASD) has been fabricated using activated charcoal (AC) as negative electrode and CoSn(OH)6/MnO2 as positive electrode to deliver an outstanding energy density of 13.12 W h kg−1 at power density of 24,000 W kg−1. As a result, 1.4 V LED was lighten up to 52 s during the discharge of AASD device. Besides, the OER activity was analyzed in three electrode configuration. Interestingly, CoSn(OH)6/MnO2 offers a very low overpotential of 270 mV to reach the current density of 10 mA cm−2 in water splitting reaction. © 2020 Elsevier Ltd