| With increasing population and the living level constantly enhancing,the demand and dependence on resource continue to rise.Nowadays,fossil fuel remains the main form of energy supplies,such as petroleum,natural gas and coal.And with energy consumption being increasing,environment pollution due to emissions of theexcessive amounts of air pollutionhas become a global issue that people cannot neglect,anymore.It is an inevitable tendency that developing reliable,low-cost and sustainable clean energy,such as wind energy,solar energy,tidal energy and geothermal power.As a kind of effective methods,electrolysis of water can produce high purity hydrogen.But the low output efficiency and geographical environment restrict the large-scale use of above-mentioned forms of energy.Hydrogen,a cleanenergy carrier,startedto enter the public’s awareness.Hydrogen is not only used directly as a kind of energy forms also can transform into other forms of energy,such as electrical energy by utilizing fuel cells.And in process of using hydrogen,there is more effective and not the emission of air pollution.But the lack of highly effective,inexpensive and stablecatalysts for hydrogen evolution reaction(HER)becomes the crucial factor which severely restricts the large-scale application of hydrogen.Hydrogen adsorption energy(△GH*)for MoS2 is close to Pt-group metals’.But as a kind of semiconductor materials,it has a relatively poor electrical conductivity.And there is the interaction of van der Waals forces between layers of MoS2 which results in the aggregation of MoS2 layers and reduces the number of exposed active sites for HER.Considering all these factors,the HER performance of MoS2 has a severe impact.Graphene,an emergingclass of materials,has many merits and value,such as good flexibility,high specific surface area and good electrical.As a kind of ideal substrates,graphene can support MoS2 layers with increased active edge sites,suppressing the aggregation of MoS2 layers and enhancing electron transport for HER.In addition,heteroatom-doped(B,N,P and S)graphene can change the electronic structure of graphene improving electron mobility and induce a bandgap in graphene to generate active sites for HER.On the other hand,on the basis of literatures,transition metals-doped(Co,Ni,Fe,Cu)MoS2 can further improve electrocatalytic activity of MoS2 for HER.In this paper,the HER activity of MoS2/graphene hybrids is further improved by Ni-doped MoS2 or B-doped graphene.The characterization and HER performance of the hybrids also were researched.The main methods,procedures and conclusion are shown below:(1)Ni-dopedMoS2/graphene hybrids(Ni-MoS2/G)are fabricated through one-pot hydrothermal process in the presence ofNi(CH3COOH)2·4H2O and GO nanosheets.In the meantime,we also explored that Ni-doped has an impact on HER performance by changing Ni(CH3COOH)2·4H2O content.The result shows that the introduction of Ni(CH3COOH)2·4H2O can led to generation of NiMoS phase and change the morphology of hybrids,which enchanced HER activity of MoS2/G hybrids.Especially,when 0.075 mmol Ni(CH3COOH)2·4H2O was added into the hydrothermal reaction system,the Ni0.05-MoS2/G hybrid exhibited an onset potential of 165 mV,a low Tafel slope of 50.8 mV/dec and showed a fine durability after 1000 cycles without obvious attenuation of HER performance.(2)We fabricated the MoS2/B-doped graphene hybrids by one-pot facile hydrothermal route and researched the electrocatalytic activity to wards HER.The B atoms doped into the framework of RGO can change the electronic properties of graphene and electrical conductivity,generate extra holes within the valence band of the RGO and induce a bandgap in graphene which can produce active HER sites.The hybrids exhibited high HER performances under the synergistic effect of MoS2 nanosheets and B-doped RGO.Especially,the MoS2/BRGO-2 hybrid fabricated with 2.0 mmol H3BO3 exhibited a fine electrocatalytic activity for HER with a low onset potential of 130 mV,a small Tafel slope of 46.3 mV/dec and charge transfer resistance(Rct)of 87Ω at η=150mV in 0.5 MH2SO4. |
