Identification of Key Reversible Intermediates in Self-Reconstructed Nickel-Based Hybrid Electrocatalysts for Oxygen Evolution

The oxygen evolution reaction (OER) has been explored extensively for reliable hydrogen supply to boost the energy conversion efficiency. The superior OER performance of newly developed non-noble metal electrocatalysts has concealed the identification of the real active species of the catalysts. Now, the critical active phase in nickel-based materials (represented by NiNPS) was directly identified by observing the dynamic surface reconstruction during the harsh OER process via combining insitu Raman tracking and exsitu microscopy and spectroscopy analyses. The irreversible phase transformation from NiNPS to alpha-Ni(OH)(2) and reversible phase transition between alpha-Ni(OH)(2) and gamma-NiOOH prior to OER demonstrate gamma-NiOOH as the key active species for OER. The hybrid catalyst exhibits 48-fold enhanced catalytic current at 300mV and remarkably reduced Tafel slope to 46mVdec(-1), indicating the greatly accelerated catalytic kinetics after surface evolution.