Insight into the Boosted Electrocatalytic Oxygen Evolution Performance of Highly Hydrophilic Nickel-Iron Hydroxide

Nickel-iron based materials are well-known catalysts for the oxygen evolution reaction (OER) and have been widely investigated. However, the synergy between these two components is still controversial. Herein, we report a facile immersion method for the synthesis of binder-free nickel-iron hydroxide loaded on Ni foam (NiFe-OH/NF) with superior hydrophilic property and high OER catalytic activity. The strong hydrophilic property of the binder-free NiFe-OH/NF electrode significantly enhances an effective contact between electrocatalyst and aqueous electrolyte and favors the bubble detachment from the electrode, facilitating the electron transfer and improving the OER activity. The hydrophilic NiFe-OH/NF can achieve a geometrical current density of 100 mA cm^-1 at an extremely low overpotential (219 mV), along with a Tafel slope of 56 mV dec^-1 and superior long-term stability at high current density in alkaline media, strongly indicating that the hydrophilicity plays an important role in improving the OER performance in the NiFe-OH/NF.