Synergistic Effect of N-Doped Carbon and Mn in NiFe LDH To Achieve 1 A cm^–2 Current Density for the Oxygen Evolution Reaction

The development of highly efficient oxygen evolution reaction (OER) electrocatalysts is pivotal to enhance the performance of alkaline water electrolyzers. Herein, a facile two-step electrodeposition method is developed for the fabrication of nitrogen-doped carbon (NC) and manganese-incorporated NiFe layered double hydroxides (LDHs) supported on Ni foam (NF). When evaluated in 1.0 M KOH solution, the optimized material of NC₂₀-Mn-NiFe LDH showed excellent OER performance requiring low overpotentials of 298 and 331 mV to achieve high current densities of 500 and 1000 mA cm^-2, respectively, and no loss in current density was observed at fixed potentials of 1.53 and 1.57 V for 125 h in each case. This performance is not only better than that of the state-of-the-art RuO₂/NF but also most of the recently reported LDH-based catalysts. Such a remarkable performance is mainly attributed to the vertical growth of NC₂₀-Mn-NiFe LDH sheets on NF, facilitated electron transfer and charge density modulation on the active metal sites due to the electron-withdrawing and electron-donating effects of NC and Mn, respectively, resulting in the shift of the rate-determining step from OOH* formation to O₂ desorption with decreased free energy. This research work provides further insights into modulating the structure of LDH-based materials to achieve a high OER performance delivering industrial-level current densities at low overpotentials.