Reconstructed β-NiOOH enabling highly efficient and ultrastable oxygen evolution at large current density

As the active phase for most nickel-based electrodes in oxygen evolution (OER), nickel (oxy)hydroxides (NiOOH) suffer from insufficient electrochemical stability at large-current OER process due to the preferred redox into γ phase with limited charging reversibility. Herein, the reconstruction of β-NiOOH is enabled at large-current OER through constructing FeS2@NiS2 heterostructure to induce electronic-rich environment around Ni sites. By coupling with the FeS2 reconstructed FeOOH, the β-NiOOH@FeOOH is achieved as actual active phase for OER and features much superior electrochemical performance and stability over pristine NiS2 reconstructed γ-NiOOH, with the ultralow overpotential of 220 mV at 200 mA cm–2 and 150 h stably operating at large current. Revealed by DFT calculation, the strong electronic interaction at β-NiOOH@FeOOH interface not only enhances the electronic conductivity of NiOOH, but also tunes the d-band center of Ni-d orbitals and thus optimizing the binding strength of oxygen-containing intermediates for accelerated OER kinetics.