▎ 摘　　要

Oxygen evolution is the vital and limiting reaction in electrochemical water splitting because of the sluggish kinetics and searching efficient nonprecious metal electrocatalysts is a crucial demand to obtain sustainable and clean fuels. Transition metal borides have recently attracted increasing attention as promising catalysts for oxygen evolution reaction. Herein, ultrathin Ni-Co-B nanosheets have been vertically aligned on reduced graphene oxide as exceptionally efficient oxygen evolution reaction electrocatalyst for the first time. Controlled experiments indicate the critical role of reduced graphene oxide in guiding the formation of Ni-Co-B nanosheet. The catalyst affords a current density of 10 mA cm(-2) at low overpotential of 280 mV, which is better than most of metal boride catalysts reported to date. Stable current output is maintained at 20 mA cm(-2) for at least 60 h. We expect this work will arouse the interests on design of compositing two-dimensional metal borides with graphene, C3N4, and metal dichalcogenides towards applications in energy storage and conversion, electrocatalysis, and sensing. (C) 2018 Elsevier B.V. All rights reserved.