Porous cauliflower-like nanoarchitectures of NiMn-layered double hydroxide as a promising electrode for oxygen evolution reaction and supercapacitor applications

As fossil fuel reserves diminish and the global population accelerating, there has been a significantly increased demand of alternative energy generation and storage technologies. To do so researchers are in search of the prominent and efficient multifunctional electrode materials. Therefore, in this study we synthesized cauliflower-like nanoarchitectures of nickel-manganese layered double hydroxide (NiMn-LDH) on porous nickel foam (NF) via hydrothermal method. We thoroughly examined the influence of the Ni / Mn molar ratios on the structural, morphological, and electrochemical properties. Among all the studied NiMn-LHDs, the highest specific capacitance of 1005 F/g at a current density of 1 mA/cm² in 1 M KOH electrolyte is obtained by the sample Ni₇₅Mn₂₅-LDH. Additionally, it demonstrates long-term cycling stability of 3000 cycles (72.7 % capacity retention) with negligible capacity loss of 0.009 % in each cycle. Furthermore, Ni₇₅Mn₂₅-LDH exhibits excellent oxygen evolution reaction characteristic with lowest overpotential of 296 mV at a current density of 10 mA/cm² and a Tafel slope of 86 mV/dec demonstrating favorable reaction kinetics. The electrode also maintained excellent electrochemical stability under continuous operation of the OER for over 50 h with minimal increase of overpotential. Thus, the work demonstrates the avenue to develop efficient electrode materials for supercapacitor and water splitting applications.