Synergizing in-grown Ni3N/Ni heterostructured core and ultrathin Ni3N surface shell enables self-adaptive surface reconfiguration and efficient oxygen evolution reaction

Searching for highly active, alkaline-stable and low-cost non-noble metal-based oxygen evolution reaction (OER) catalysts with disruptively low overpotential and outstanding overall performance is of great value and yet considerable challenge, due to the sluggish OER kinetics reported for almost all known materials systems. To accelerate the sluggish OER kinetics by a self-adaptive surface reconfiguration approach, herein, we have purposely designed a strongly coupled [email protected] nanostructured precatalyst consisting of an in-grown Ni3N/Ni heterostructured core and an ultrathin Ni3N shell (Ni3N/[email protected]3N) via a step-by-step thermal nitridation route. The Ni3N/[email protected]3N thus-obtained delivers an ultralow overpotential (η) of 229 mV at 10 cmgeo−2, with the remarkable 17-, 37- and 20-fold enhancements in catalytic current density per active surface area at η = 270 mV, compared favorably to the invidivual Ni3N and Ni alone as well as the commercial RuO2, respectively, together with a much reduced Tafel slope of 55 mV dec−1. In reponse to the change in applied potential to the Ni3N/[email protected]3N precatalyst during the OER process, a self-adaptive surface reconfiguration into NiOOH species takes place, which is responsible for the high catalytic activity observed. It is also evidenced by both the in-situ Raman spectrometry and ex-situ electron microscopy studies. To further support the experimental observation, density functional theory (DFT) calculations demonstrate that the interfacial electron transfer from NiOOH to Ni3N produces positive-charged Ni cations as the highly active sites to substantially lower the energy barriers for adsoprtion/desportion of the OER intermediates.