Preparation Of Graphene(Type)-Based Electrocatalysts For Hydrogen Evolution Reaction

With the increasing of world energy crisis,it is urgent to develop renewable and clean energy alternatives.Hydrogen serves as one of the most promising candidates for replacing petroleum fuels in the future.Electrolysing water is seem as one of the efficient ways to produce hydrogen.Up to now,the most effective electrocatalysts for hydrogen evolution reaction are based on Pt-group metals.However,as we know,Pt-group metals are very scarce in the earth and extremely expensive.Scientists have been trying to reduce the Pt content or design Pt-free catalyst which are also very active for hydrogen evolution reaction to substitute Pt-group metals.Based on the aforementioned goal,the details are summarized as follows:?1?A three-dimensional?3D?reduced graphene oxide-Mn₃O₄ nanosheet?rGO/Mn₃O₄?hybrid was achieved by simple electrodeposition technique.Small palladium nanoparticle were homogeneously anchored onto rGO/Mn₃O₄ substrate through the reduction of palladium salt.The interpenetrating network architecture of rGO/Mn₃O₄ greatly inhibited the aggregation of 2D sheets of Mn₃O₄ and rGO,and the open 3D orientation of the rGO/Mn₃O₄ hybrid nanosheets on the electrode facilitated both mass transport and electron transfer as well as maximally exposed active sites.The introduction of Mn₃O₄ enhanced the structural and electrochemical stability of rGO.The as-synthesized rGO/Mn₃O₄-Pd hybrid was employed as an electrocatalyst for electrocatalytic hydrogen evolution reaction?HER?.The electrocatalyst showed a low overpotential of 20 mV at 10 mA·cm-2,a small Tafel slope of 48.2 mV·dec-1,and a large exchange current density of 0.59 mA·cm-2.Importantly,the catalyst possessed superior durability with 85.87%of catalytic activity after a long-time test?10 h?.?2?In this study,an interlayer spacing expanded counterpart,ammonia-intercalated MoS₂ was obtained by a simple hydrothermal reaction of ammonium molybdate and elemental sulfur in hydrazine monohydrate solution.Then,the ammonia-intercalated MoS₂ could be easily exfoliated by ultrasonication to get monolayer MoS₂.Importantly,these monolayer MoS₂ possessed rich S vacancies.The produced MoS₂ demonstrated a proliferated active site density as well as low-loss electrical transport for efficiently electrochemical hydrogen production from water.Computational studies prove that the S vacancies enabled the inert basal planes by introducing localized donor states in the bandgap and lowered the hydrogen adsorption free energy.As is expected,the monolayer MoS₂ with S vacancy exhibited an excellent electrocatalytic hydrogen evolution reaction performance with a low overpotential?at 10 mA·cm-2?of 160 mV?V vs RHE?in acid media and a small Tafel slope of 54.9 mV·dec-1.Furthermore,the catalyst displayed a good long-term stability and chemical stability during electrochemical hydrogen production process.