In Situ Synthesis of Bifunctional NiMn Hybrid Oxides for High-Performance Flexible Supercapacitors and Oxygen Evolution Reaction

Abstract

Ni-based binary alloy compositions are considered promising materials for energy storage and catalysis applications. Herein, a highly simplistic and efficient technique is reported for synthesizing NiMn hybrid oxyhydroxides as a bifunctional electrode for flexible supercapacitors and an efficient oxygen evolution reaction (OER) catalyst. The synthesis approach involves Ni and Mn coelectrodeposition under a controlled oxygenated environment over a flexible stainless-steel substrate. The developed electrodes exhibit an excellent specific capacitance of 633.54 F g⁻¹ at a current density of 1 A g⁻¹, matching one of the best-reported values in the literature. A symmetric device demonstrates a remarkable energy density of 45 Wh kg⁻¹ at a power density of 181.22 W kg⁻¹. The device shows an excellent cyclic stability of 89.5% after 10 000 cycles. In addition, the NiMn oxyhydroxide electrode showed a remarkable performance in OER with overpotential values of only 282 and 312 mV at 500 and 1000 mA cm⁻² current density, surpassing many well-reported studies in the literature. The current study provides a facile and efficient strategy for synthesizing bifunctional electrodes for high-performance energy storage devices and catalysts for OERs.