Oxygen vacancy of the catalyst is one of the most significant factors affecting the oxygen evolution reaction (OER) electrocatalysis, a key process for overall water splitting. Here, we report the oxygen vacancy engineering of Co(OH)(2) hexagonal nanoplates by doping Ni element, which can efficiently lower the average Co oxidation state and thus optimize the Gibbs free energy of the intermediates, giving rise to the largely promoted OER performances. Impressively, the as-obtained oxygen-vacancy-rich Ni-doped Co (OH)(2) hexagonal nanoplates manifest OER overpotential as low as 238 mV at 10 mA cm(-2) in 1 M KOH solution, being superior to most of binary CoNi hydroxides. In accordance with the high OER activity, it also displays excellent durability in strong alkaline media over 40 h, presenting an advanced electrocatalyst for OER. (C) 2019 Published by Elsevier Inc.