Fine-tuning electronic structure of N-doped graphitic carbon-supported Co- and Fe-incorporated Mo2C to achieve ultrahigh electrochemical water oxidation activity

Abstract

Mo₂C is an excellent electrocatalyst for hydrogen evolution reaction (HER). However, Mo₂C is a poor electrocatalyst for oxygen evolution reaction (OER). Herein, two different elements, namely Co and Fe, are incorporated in Mo₂C that, therefore, has a finely tuned electronic structure, which is not achievable by incorporation of any one of the metals. Consequently, the resulting electrocatalyst Co_0.8Fe_0.2–Mo₂C-80 displayed excellent OER catalytic performance, which is evidenced by a low overpotential of 214.0 (and 246.5) mV to attain a current density of 10 (and 50) mA cm⁻², an ultralow Tafel slope of 38.4 mV dec⁻¹, and long-term stability in alkaline medium. Theoretical data demonstrates that Co_0.8Fe_0.2–Mo₂C-80 requires the lowest overpotential (1.00 V) for OER and Co centers to be the active sites. The ultrahigh catalytic performance of the electrocatalyst is attributed to the excellent intrinsic catalytic activity due to high Brunauer–Emmett–Teller specific surface area, large electrochemically active surface area, small Tafel slope, and low charge-transfer resistance.