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

Abstract

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 core@shell nanostructured precatalyst consisting of an in-grown Ni 3 N/Ni heterostructured core and an ultrathin Ni 3 N shell (Ni 3 N/Ni@Ni 3 N) via a step-by-step thermal nitridation route. The Ni 3 N/Ni@Ni 3 N thus-obtained delivers an ultralow overpotential ( η ) of 229 mV at 10 cm geo −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 Ni 3 N and Ni alone as well as the commercial RuO 2 , respectively, together with a much reduced Tafel slope of 55 mV dec −1 . In reponse to the change in applied potential to the Ni 3 N/Ni@Ni 3 N 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 Ni 3 N produces positive-charged Ni cations as the highly active sites to substantially lower the energy barriers for adsoprtion/desportion of the OER intermediates. • Core@shell nanostructured Ni 3 N/Ni@Ni 3 N was proposed by a step-by-step nitridation. • A self-adaptive surface reconfiguration into NiOOH takes place during OER. • Interfacial electron transfer from NiOOH to Ni 3 N lowers the energy barriers. • Ni 3 N/Ni@Ni 3 N delivers an ultralow overpotential of 229 mV at 10 mA cm −2 . • In-grown and core@shell nanostructures provide effective electron transfer pathway.