Borate ion-intercalated Ni Fe layered double hydroxide (Ni Fe LDH) is synthesized as a highly active electrocatalyst toward oxygen evolution reaction (OER) for the first time. With the intercalation of borate ions, the interlayer spacing and specific surface area of the Ni Fe LDH are increased, meanwhile the pore size distribution shifts to a larger pore size range. The borate ion-intercalated catalyst prepared at 20% of Fe content in presence of 0.05 M sodium borate additive exhibits the highest OER electrocatalytic activity, which shows a low onset overpotential of 270 mV and a Tafel slope of 42 mV dec(-1). The high catalytic activity of intercalated OER catalyst can be attributed to the enhanced mass transport and charge transfer as well as the increased specific surface area due to the borate ion intercalation. In addition, the intercalated borate ions act as a proton-accepting agent help to promote O-O bond formation during OER. This work would open up a novel strategy for the synthesis of ion-intercalated layered materials for high-performance water splitting applications. (C) 2018 Elsevier Inc. All rights reserved.