Phase Locking of NiOOH@β-Ni(Fe)OOH Reconstructed Simultaneously for Robust Oxygen Evolution at High Current Density

Electrochemical oxygen evolution reaction usually induces the reconstruction of NiFe layered double hydroxides (LDH) into β-Ni(Fe)OOH, which further undergoes detrimental overcharging into γ-Ni(Fe)OOH with low activity under high-potential and high-current density conditions. In this study, simultaneous reconstruction of the NiMoO₄@NiFe LDH (NMO@NFL) into NiOOH@β-Ni(Fe)OOH enables maintaining the activity and stability of β-Ni(Fe)OOH. An ultralow overpotential of 203 mV is required to achieve a current density of 10 mA cm^-2. In the anion exchange membrane water electrolyzer(AEMWE), a current density of 1 A cm^-2 is achievable at 1.81 V. The NiOOH@β-Ni(Fe)OOH demonstrates significantly enhanced stability with a degradation rate of merely 1.86 mV h^-1 at 1 A cm^-2, which is over 9.5 times lower than that of the γ-Ni(Fe)OOH phase reconstructed from individual NiFe LDH (17.7 mV h^-1). In situ Raman spectroscopy and density functional theory (DFT) calculation demonstrate that the heterogeneous interface effectively suppresses the overcharging of β-Ni(Fe)OOH into γ-Ni(Fe)OOH through interfacial electron donation. These findings provide crucial insights into achieving phase locking and improving stability of simultaneously reconstructed heterogeneous materials, presenting a reliable pathway for the further development of efficient and durable electrocatalysts.