Composition dependent electrocatalytic activity of Ni(OH)2-graphene hybrid catalyst deposited by one-step vacuum kinetic spray technique

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.