Partially crystallized Ni–Fe oxyhydroxides promotes oxygen evolution

Abstract

The slow oxygen evolution reaction (OER) kinetics influences hydrogen production efficiency from water splitting. To break through the bottleneck of water splitting, it is urgent to develop efficient and economic electrocatalysts. Although NiFe-based catalysts exhibit outstanding OER activity, the complicated preparation process limits their large-scale synthesis and applications. Here, partially crystallized nickel-iron oxyhydroxides are synthesized by a facile sol-gel method. When the Fe/Ni mole ratio is 0.5:1, the NiFe0.5(OH)x catalyst shows superior OER performance with a low OER overpotential of 265 mV and good durability. Kinetic studies show that the energy barrier of NiFe0.5(OH)x is only 31.5 kJ mol−1, much smaller than those of Ni(OH)x (41.0 kJ mol−1) and Fe(OH)x (44.8 kJ mol−1). The synergistic action between Ni and Fe sites not only facilitates mass and charge transfer, but also promotes the formation of ∗OOH intermediate for the OER.