Composition-Tunable Co_3–xFe_xMo₃N Electrocatalysts for the Oxygen Evolution Reaction

The sluggish OER kinetics necessitates the development of highly active and durable electrocatalysts; however, an ideal alternative to expensive Ir/Ru-based and poorly conductive metal-oxide-based catalysts is absent. Herein, we demonstrate the class of nitrides prototype of Co 3– x Fe x Mo 3 N (0 ≤ x ≤ 3). These nitrides are cost-effective and highly conductive and have favorable composition flexibility. The optimized Co 2.5 Fe 0.5 Mo 3 N shows a mere overpotential of 218 mV at 10 mA cm geo –2 and a robust durability at 100 mA cm geo –2 over a 90-h measurement. Impressively, the water electrolyzer of Pt/C∥Co 2.5 Fe 0.5 Mo 3 N only requires a cell voltage of 1.52 V to afford 10 mA cm geo –2 . XPS spectra and DFT calculation reveal that the partial Fe substitution not only increases the content of the active Co 3+ species of Co 2.5 Fe 0.5 Mo 3 N but also upshifts the d band center of the Co site toward the Fermi level, which leads to the lower absorption energy of oxygen intermediates and hence substantially promotes the OER activity.