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.