Mesoporous spinel NiFe oxide cubes as advanced electrocatalysts for oxygen evolution

Abstract

Oxygen evolution reaction (OER) is the rate-controlling step of the electrochemical water splitting. The slow kinetics hinders large-scale H2 production. Herein, the spinel NiFe oxides were prepared by directly pyrolyzing nickel hexacynoferrate precursors in air. The NiFe oxides were presented as mesoporous nanocubes with a specific surface area of 125 m2 g−1. The mesoporous spinel NiFe oxide nanocubes can afford a geometric current of 10 mA cm−2 at a low overpotential of a 0.24 V and a small Tafel slope of 41 mV dec−1 in alkaline solution. The specific activity can reach up to 0.37 mA cm−2 with a turnover frequency of 0.93 s−1. The superior OER activity of the NiFe oxide nanocubes (NiFeO NCs) can outperform those of the state-of-the-art IrO2 catalysts, and compare favorably with other spinel transition metal oxides reported recently under identical condition. NiFeO NCs also show a long-term durability without significant loss of the OER activity. Our works provide a new strategy to develop efficient, robust and earth-abundant spinel NiFe oxides as advanced OER electrocatalysts to replace the expensive commercial IrO2 catalysts for water splitting in the industrial scale.