Surface reconstruction induced in situ phosphorus doping in nickel oxides for an enhanced oxygen evolution reaction

Surface reconstruction of non-oxide electrocatalysts for the oxygen evolution reaction (OER) to form "true" active species has been reported; however, the mechanism of the in situ surface activation has remained unclear. In this work, nanocrystalline Ni5P4 is prepared as a pre-catalyst for the OER to gain insight into the in situ surface activation. We find that NiO nanosheets with abundant crystal defects are formed on the surfaces of Ni5P4 particles during the electrochemical process. The effects of the in situ P incorporation in surface reconstruction derived NiO for OER electrocatalysis are discussed. Theoretical calculations reveal that the heteroatom P substitution for O atoms of NiO crystals on the subsurface can weaken the binding strength of the OER intermediates, change the potential-determining step of the OER and achieve a lower theoretical overpotential. The present work provides a novel mechanism of the enhanced electrocatalytic performances of non-oxide materials for OER electrocatalysis by highlighting the effects of surface reconstruction induced in situ heteroatom doping in derived active materials.