Big to Small: Ultrafine Mo2C Particles Derived from Giant Polyoxomolybdate Clusters for Hydrogen Evolution Reaction

Due to its electronic structure, similar to platinum, molybdenum carbides (Mo2C) hold great promise as a cost-effective catalyst platform. However, the realization of high-performance Mo2C catalysts is still limited because controlling their particle size and catalytic activity is challenging with current synthesis methods. Here, the synthesis of ultrafine beta-Mo2C nanoparticles with narrow size distribution (2.5 +/- 0.7 nm) and high mass loading (up to 27.5 wt%) on graphene substrate using a giant Mo-based polyoxomolybdate cluster, Mo-132((NH4)(42)[MO132O372(CH3COO)(30)(H2O)(72)]center dot 10CH(3)COONH(4)center dot 300 H2O) is demonstrated. Moreover, a nitrogen-containing polymeric binder (polyethyleneimine) is used to create Mo-N bonds between Mo2C nanoparticles and nitrogen-doped graphene layers, which significantly enhance the catalytic activity of Mo2C for the hydrogen evolution reaction, as is revealed by X-ray photoelectron spectroscopy and density functional theory calculations. The optimal Mo2C catalyst shows a large exchange current density of 1.19 mA cm(2), a high turnover frequency of 0.70 s(-1) as well as excellent durability. The demonstrated new strategy opens up the possibility of developing practical platinum substitutes based on Mo2C for various catalytic applications.