Graphite Nanoflake-Modified Mo2C with Ameliorated Interfacial Interaction as an Electrocatalyst for Hydrogen Evolution Reaction

Molybdenum carbide (Mo2C) is anticipated to be a promising electrocatalyst for electrocatalytic hydrogen production due to its low cost, resourceful property, prominent stability, and Pt-like electrocatalytic activity. The rational design of Mo2C-based electrocatalysts is expected to improve hydrogen evolution reaction (HER) performance, especially by constructing ultrasmall Mo2C particles and appropriate interfaces. Herein, composites of molybdenum carbide (Mo2C) quantum dots anchored on graphite nanoflakes (Mo2C/G) were fabricated, which realized a stable overpotential of 136 mV at 10 mA cm-2 for the HER with a small Tafel slope of 76.81 mV dec-1 in alkaline media, and operated stably over 10 h and 2000 cycles. The superior HER performance can be attributed to the fact that graphite nanoflakes could act as a matrix to disperse Mo2C as quantum dots to expose more active sites and guarantee high electronic conductivity and, more importantly, provide ameliorated interfacial interaction between Mo2C and graphite nanoflakes with appropriate hydrogen binding energy and charge density distribution. To further explore which kind of interfacial interaction is more favorable to improve the HER performance, density functional theory calculations and corresponding contrast experiments were also performed, and it was interesting to prove that Mo2C quantum dots anchored to the basal planes of defective graphite nanoflakes exhibit better electrochemical performance than those anchored on the edges.