Surface Phase Engineering Modulated Iron-Nickel Nitrides/Alloy Nanospheres with Tailored d-Band Center for Efficient Oxygen Evolution Reaction.

The oxygen evolution reaction (OER) plays a key role in many electrochemical energy conversion systems, but it is a kinetically sluggish reaction and requires a large overpotential to deliver appreciable current, especially for the non-noble metal electrocatalysts. In this study, the authors report a surface phase engineering strategy to improve the OER performance of transition metal nitrides (TMNs). The iron-nickel nitrides/alloy nanospheres (FeNi3 -N) wrapped in carbon are synthesized, and the optimized FeNi3 -N catalyst displays dual-phase nitrides on the surface induced by atom migration phenomenon, resulting from the different migration rates of metal atoms during the nitridation process. It shows excellent OER performance in alkaline media with an overpotential of 222 mV at 10 mA cm-2 , a small Tafel slope of 41.53 mV dec-1 , and long-term durability under high current density (>0.5 A cm-2 ) for at least 36 h. Density functional theory (DFT) calculations further reveal that the dual-phase nitrides are favorable to decrease the energy barrier, modulate the d-band center to balance the absorption and desorption of the intermediates, and thus promote the OER electrochemical performance. This strategy may shed light on designing OER and other catalysts based on surface phase engineering.