LAUSR

Abstract Ni(OH)2-graphene hybrid bifunctional catalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) were deposited on Ni foam from low cost and abundant micro-sized particles of Ni(OH)2 and graphite powders using modified vacuum spray technique. The deposited thin films exhibited a mixed morphology of nanosheets and nanoflakes. We investigated the effect of increasing Ni(OH)2 content on the electrocatalytic activity toward the OER and the HER in 1 M KOH. We found that the hybrid catalyst with low Ni(OH)2 content (20 wt%) revealed a high OER electrocatalytic activity that delivers 50 mA cm−2 at an overpotential of 330 mV with a low Tafel slope of 78 mV dec−1. Meanwhile, catalysts with higher Ni(OH)2 content (80 wt%) exhibited superior HER activity that delivered 20 mA cm−2 at an overpotential of 154 mV and a low Tafel slope of 92 mV dec−1. The long term stability for both working electrodes was verified up to 25 h.