Composition-Tunable\nCo_3–<i>x</i>Fe_<i>x</i>Mo₃N Electrocatalysts\nfor the Oxygen Evolution Reaction

Abstract

The sluggish OER kinetics necessitates the development\nof highly\nactive and durable electrocatalysts; however, an ideal alternative\nto expensive Ir/Ru-based and poorly conductive metal-oxide-based catalysts\nis absent. Herein, we demonstrate the class of nitrides prototype\nof Co_3–<i>x</i>Fe_<i>x</i>Mo₃N (0 ≤ <i>x</i> ≤ 3).\nThese nitrides are cost-effective and highly conductive and have favorable\ncomposition flexibility. The optimized Co_2.5Fe_0.5Mo₃N 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,\nthe water electrolyzer of Pt/C∥Co_2.5Fe_0.5Mo₃N only requires a cell voltage of 1.52 V to afford\n10 mA cm_geo^–2. XPS spectra and DFT calculation\nreveal that the partial Fe substitution not only increases the content\nof the active Co³⁺ species of Co_2.5Fe_0.5Mo₃N but also upshifts the d band center of the Co site\ntoward the Fermi level, which leads to the lower absorption energy\nof oxygen intermediates and hence substantially promotes the OER activity.