Hybrid Nanostructured Compounds of Mo2C on Vertical Graphene Nanoflakes for a Highly Efficient Hydrogen Evolution Reaction

Organizing a post-fossilfuel economy requires the developmentof sustainable energy carriers. Hydrogen is expected to play a significantrole as an alternative fuel as it is among the most efficient energycarriers. Therefore, nowadays, the demand for hydrogen productionis increasing. Green hydrogen produced by water splitting produceszero carbon emissions but requires the use of expensive catalysts.Therefore, the demand for efficient and economical catalysts is constantlygrowing. Transition-metal carbides, and especially Mo2C,have attracted great attention from the scientific community sincethey are abundantly available and hold great promises for efficientperformance toward the hydrogen evolution reaction (HER). This studypresents a bottom-up approach for depositing Mo carbide nanostructureson vertical graphene nanowall templates via chemical vapor deposition,magnetron sputtering, and thermal annealing processes. Electrochemicalresults highlight the importance of adequate loading of graphene templateswith the optimum amount of Mo carbides, controlled by both depositionand annealing time, to enrich the available active sites. The resultingcompounds exhibit exceptional activities toward the HER in acidicmedia, requiring overpotentials of 82 mV at -10 mA/cm(2) and demonstrating a Tafel slope of 56 mV/dec. The high double-layercapacitance and low charge transfer resistance of these Mo2C on GNW hybrid compounds are the main causes of the enhanced HERactivity. This study is expected to pave the way for the design ofhybrid nanostructures based on nanocatalyst deposition on three-dimensionalgraphene templates.