Dynamic self-optimization of hierarchical NiAl architecture catalysing oxygen evolution reaction in alkaline water electrolysis

Engineering highly active earth-abundant oxygen evolution electrode (OEE) with a promising method for alkaline water splitting is an extraordinarily honorable challenge. In this work, a facile and effective strategy has been developed to obtain a self-supported OEE (marked as HNA-CA-ECA) with defect-rich (Ni(OH)2/NiOOH hybrid) nanosheets that serve as the active sites, in situ generating over an equally important electrically conductive NiAl with hierarchical architecture to drive proficient catalysis. Notably, the HNA-CA-ECA catalyst shows superior activity toward OER with the overpotentials of 193 mV to reach a geometrical catalytic current density of 10 mA/cm2 with a very low Tafel slope of 39 mV/dec, surpassing the performance of the-state-of-the art IrO2, which requires an overpotential of 216 mV yielding catalytic current density of 10 mA/cm2 with a Tafel slope of 65 mV/dec. Interestingly, there was no significant performance loss of the HNA-CA-ECA catalyst after continuous 168 h electrolysis operation at a high current density of 800 mA/cm2 with an ultra-low overpotential of 229 mV in 6 M KOH at 353 K. Such a remarkable feature lies in the synergistic effect of the engineered high intrinsic activity, extremely huge catalytic surface area, and accelerated electron/ion transport. Moreover, the novel methodology of integrating the defect-rich nickel (oxy) hydroxide nanosheets (crystal defects) and formation of hierarchically porous architecture (morphology defects) presented in this work can broaden horizons and provide new dimensions in the design of highly active and stable electrocatalysts for alkaline water electrolysis.