Promotion of electrochemical oxygen evolution reaction by chemical coupling of cobalt to molybdenum carbide

Herein, we report a novel strategy to promote electrochemical oxygen evolution reaction (OER) on cobalt (Co) surface by coupling Co to molybdenum carbide (Mo₂C). Chemically coupled Co and Mo₂C nanoparticles were synthesized through a simple heat treatment of the mixture containing Co and Mo precursors and graphitic carbon nitride (g-C₃N₄). Transmission electron microscopy (TEM) images obviously showed that Co and Mo₂C nanoparticles were coupled at Co/Mo₂C interfaces. X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculation results revealed that electrons were transferred from Co to Mo₂C nanoparticles across the interfaces. The electron transfer makes the Co surface more electrophilic by d-band center of Co upshift, leading to an increase in OH⁻ affinity. As a result, the Co nanoparticles coupled with Mo₂C have OER-favorable Co-oxo and Co-hydroxo configuration within their oxidized surfaces, and hence, can accelerate the overall OER than bare Co nanoparticles. This work demonstrates that the Co nanoparticles chemically coupled to Mo₂C exhibited excellent OER activity and stability in an alkaline electrolyte and suggests a promising way to design an active OER catalyst.