Strong covalent catalyst-support interactions have been utilized extensively to tailor the ensemble geometry and electronic properties of active sites in heterogeneous catalysts. Supported earth-abundant catalysts, such as layered MoS_x materials adsorbed on Au disk electrodes, have shown enhanced reactivity for electrochemical hydrogen production. Although flat substrates enable reactivity comparisons, adsorbing a single monolayer of metal chalcogenide on a high surface area support is preferred because the influence of flat substrates dissipate with thicker layers. To maximize MoS_x-support interactions, this work utilizes colloidal-ligand exchange methods to synthesize single monolayer Au@MoS₄ core-shell catalysts by adsorbing tetrathiomolybdate (MoS₄^2-) complexes onto Au nanoparticles. Through a combination of spectroscopic techniques and computational methods, we find that strong hybridization between Au surface and MoS₄ complexes elongates the Mo-S bonds, alters the Mo coordination environment, and templates cross-linked MoS_x oligomers on the nanoparticle surface. Intimate Au-S interactions generate highly active bridging disulfide sites and modifies the hydrogen atom adsorption energies for more efficient HER turnover. Additionally, good colloidal stability and solution dispersibility of these Au@MoS₄ nanoparticles enable their incorporation into realistic high surface area carbon fiber electrode configurations. These electrodes achieve 100 mA/cm² of HER current density at only 171 mV of overpotential, comparable to the best known MoS_x-based HER catalysts in literature.

Alexander Shumski

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