Synergizing in-grown Ni_3N/Ni heterostructured core and ultrathin Ni_3N surface shell enables self-adaptive surface reconfiguration and efficient oxygen evolution reaction

摘要

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_3N/Ni heterostructured core and an ultrathin Ni_3N shell (Ni_3N/Ni@Ni_3N) via a step-by-step thermal nitridation route.The Ni_3N/Ni@Ni_3N 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_3N 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_3N/ Ni@Ni_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 Ni_3N produces positive-charged Ni cations as the highly active sites to substantially lower the energy barriers for adsoprtion/desportion of the OER intermediates.