Nano-engineering Of Molybdenum Disulfide Towards Efficient Electrocatalysts For Hydrogen Evolution Reaction

Electrochemical hydrogen evolution reaction(HER) from water is one of the promising routes for hydrogen production, which is however severely limited by high-cost noble metal catalysts, emerging the demand of advanced catalysts with element-abundance, economic-cost and stability. Molybdenum sulfide, possessing a free energy of hydrogen adsorption(ΔGH*) approximate to that of Pt, was recently highlighted as an efficient electrocatalyst for HER on the basis of its earth-abundance and economic-cost. However, limited by its poor conductivity and uncontrolled structure of active-sites, Mo S2 usually presents unsatisfied performance far from Pt-based catalysts. Meanwhile, the current strategies towards optimized Mo S2 are precluded by the poor tunability, fussy procedures and rigid manipulation. Based on the structural features of Mo S2, this thesis proposed facile strategies, including ultrathin Mo S2 growing in in-situ formed carbon matrix, and reactant-self-shielding under microwave irradiation, to synergically improve the activity and conductivity of Mo S2, which showed the obviously promoted performance in HER.The space-confined growth by in-situ formed polysaccharides during hydrothermal process is successfully employed to fabricate ultrathin Mo S2 nanosheets, which further evolve to Mo S2/C evenly integrating nanosheets(2 ~ 4 nm) with conducting carbon after carbonization. The Mo S2/C exhibits an excellent activity for HER with a small onset overpotential of ~80 m V and a high current density of 88 m A cm-2 at η = 200 m V, which is associated with the enriched rim-sites on ultrathin Mo S2 and the improved conductivity by carbon matrix. This work demonstrates that the ultrathin Mo S2 nanosheets within carbon, possessing synergistically-enhanced activity and conductivity for HER, are feasible through the space-confined growth based on polysaccharide matrix, and this would open up new opportunities for exploiting highly efficient electrocatalysts.Meanwhile, we proposed a microwave-assisted hydrothermal routes employing reactant-self-shielding for active-site enriched Mo S2 effective edge sites. Covered by excessive thiourea the active-sites of Mo S2 have been protected in the reaction process and avoid increasing the size of nanostructure. Thiourea can be served as both a source of sulfur element and protector of active edge sites. Moreover, Exposure of active-sites by an acid-treatment to remove thiourea on the surface is crucial to enhance current density from 24 to 68 m A cm-2 at η = 300 m V.Additionally, Mo S2/PANI and Mo S2/CC are synthesized in this work, and their morphology and electrocatalytic behaviors were characterized.In summary, we proposed feasible strategies to optimize the structure of Mo S2 and consequently enhance its HER performance, in which the insightful understanding in the strusture-dependant catalytic performance was discovered. This work will shed some light on the development of efficient electrocatalysts in energy-related fields.