Microwave-assisted CVD-like synthesis ofdispersed monolayer/few-layer N-doped grapheneencapsulated metal nanocrystals for efficientelectrocatalytic oxygen evolution

摘要

Herein a novel and general microwave-assisted chemical vapor deposition (CVD)-like synthetic strategywas developed to realize the ultrafast synthesis of a series of well-dispersed monolayer/few-layer Ndoped graphene shell encapsulated metal nanocrystals (M@NC) by using a metal–organic framework(MOF) on graphene as precursors for the first time. Unlike traditional programmed heat treatment, thismicrowave-assisted method decomposed the MOF into separated metal and carbon- and nitrogencontaining gases rather than aggregated metal and carbon composites during the initial thermaltransformation stages. This change ensured the effective control of the subsequent formation process ofcarbon on the surface of metal and led to the formation of well-dispersed M@NC with monolayer/fewlayer NC. Moreover, the graphene substrate promoted the full exposure of all active monolayer/fewlayer NC, and thus the obtained FeNi@NC/graphene displays the best electrocatalytic properties for theoxygen evolution reaction of all of the previously reported M@NC based catalysts, including the lowestoverpotential (261 mV) at 10 mA cm2 in alkaline electrolyte (1 M KOH), the smallest Tafel slope(40 mV dec1) and excellent durability for at least 120 h.