MoS₂ Nanoparticles Grown on Graphene: An Advanced Catalyst for the Hydrogen Evolution Reaction

Abstract

Advanced materials for electrocatalytic and photoelectrochemical water splitting are central to the area of renewable energy. In this work, we developed a selective solvothermal synthesis of MoS(2) nanoparticles on reduced graphene oxide (RGO) sheets suspended in solution. The resulting MoS(2)/RGO hybrid material possessed nanoscopic few-layer MoS(2) structures with an abundance of exposed edges stacked onto graphene, in strong contrast to large aggregated MoS(2) particles grown freely in solution without GO. The MoS(2)/RGO hybrid exhibited superior electrocatalytic activity in the hydrogen evolution reaction (HER) relative to other MoS(2) catalysts. A Tafel slope of ∼41 mV/decade was measured for MoS(2) catalysts in the HER for the first time; this exceeds by far the activity of previous MoS(2) catalysts and results from the abundance of catalytic edge sites on the MoS(2) nanoparticles and the excellent electrical coupling to the underlying graphene network. The ∼41 mV/decade Tafel slope suggested the Volmer-Heyrovsky mechanism for the MoS(2)-catalyzed HER, with electrochemical desorption of hydrogen as the rate-limiting step.

Nickel Hydr(oxy)oxide Nanoparticles on Metallic MoS2 Nanosheets: A Synergistic Electrocatalyst for Hydrogen Evolution Reaction

“…Electrochemical impedance spectra of the 1T‐MoS 2 and the hybrid catalyst electrodes indicate that the improved HER activities in the hybrids are due to the faster electrode reaction kinetics (Figure S10, Supporting Information). The Tafel slope of 1T‐MoS 2 is determined to be ≈114 mV dec −1 , suggesting that the rate‐limiting step is the Volmer reaction of HER in alkaline media (Figure 2b) 38. However, the Tafel slopes of all the hybrid catalyst electrodes are around 75 mV dec −1 , much smaller than that of 1T‐MoS 2 , suggesting significantly improved reaction kinetics of HER in alkaline media.…”

“…Extensive efforts have been made to improve the HER activities of MoS 2 ‐based catalysts in acidic media by strategies such as nanostructure engineering,35, 36, 37, 38 defect engineering,39, 40, 41, 42, 43 phase engineering,44, 45, 46, 47, 48 and heteroatom doping49, 50, 51 to increase the number or enhance the intrinsic activity of active sites. However, little work has been reported to improve the HER activities of MoS 2 ‐based materials in alkaline media 31, 52.…”

Face the Edges: Catalytic Active Sites of Nanomaterials

“…The second rule seems easier to achieve: Jaramillo group synthesized a highly ordered double‐gyroid MoS 2 bicontinuous network with nanoscale pores, the high surface curvature exposes abundant edges47; Xie group prepared defect‐rich MoS 2 nanosheets which force the formation of edges (Figure 2b) 48. As for enhancing the conductivity, Dai group fabricated a strong coupling MoS 2 –graphene sheets, and the conducting network facilitate the catalytic reaction (Figure 2a) 49…”

“…a) MoS 2 grown on graphene can help to increase the conductivity. Reproduced with permission 49. Copyright 2011, American Chemistry Society.…”

Transition Metal‐Promoted V2CO2 (MXenes): A New and Highly Active Catalyst for Hydrogen Evolution Reaction

“…To assure a sustainable hydrogen generation, tremendous efforts have been made to develop the earth abundant and cost‐effective alternatives to Pt in the past few decades, including non‐precious metal alloys, metal chalcogenides, metal carbides, metal nitrides, metal phosphides, and so on 3, 4, 5, 6, 7, 8. Among these alternatives, 2D layered materials (such as MoS 2 ) have gained broad interest recently because of their extremely large surface areas, low cost, and excellent catalytic activity 9, 10, 11…”