Tuning Graphene Nanostructures for Incorporating Multisized Mo 2 C Particles as Electrocatalysts for Highly Efficient and Stable Hydrogen Evolution Reaction

This study involves fabricating two graphene nanostructure/multiple‐sized Mo 2 C particles nanocomposites with in situ solution plasma exfoliation as electrocatalysts for highly efficient and stable hydrogen evolution reaction (HER). 3D/0D Graphene onion/Mo 2 C (G OS Mo) and 2D/0D graphene nanosheets/Mo 2 C (G NS Mo) nanocomposites can be generated through solution plasma exfoliation in 1 M H 2 SO 4 and 1 M KOH, respectively. Both G OS Mo and G NS Mo (wt ratio Mo:C = 55:45) display graphene scaffolds incorporating multiple‐sized Mo 2 C particles with abundant interfacial areas and porosities. The G OS Mo sample shows its HER performance hierarchy in the order of 0.5M H 2 SO 4 > 1 M KOH > seawater > phosphate‐buffered saline electrolyte, correlating with their charge transfer characteristics. All four cases of G OS Mo’s HER activities display 100 h stability, indicating its versatility and robustness. The G OS Mo sample displays champion HER with an overpotential value of 134 mV at 10 mA cm −2 and a Tafel slope value of 54 mV dec −1 . The G OS Mo sample’s superior HER performances with high stability can be attributed to strong interfacial electronic couplings between Mo 2 C particles and graphene nanostructures that optimize hydrogen adsorption kinetics. This approach presents a sustainable and facile plasma exfoliation for synthesizing multidimension 3D/0D or 2D/0D of Mo 2 C/graphene nanocomposite with high HER activity and excellent HER stability.