The Research On Preparation And Hydrogen Evolution Reaction Performance Of Mo-and Ni-based Surfides(Oxides) Composites

Hydrogen energy,as renewable and clean energy,is regarded as the most ideal energy carrier.Large-scale hydrogen production via electrochemical water splitting has gradually become the promising way due to the features of high purity,no pollution and abundant raw materials.To reduce the energy comsume,it is of great practical significance to study the non-noble metal cathode materials with high catalytic activity.The current researches are mainly focused on two aspects: selecting non-noble metal materials with high catalytic activity to decrease the overpotential for hydrogen evolution reaction?HER?,increasing the surface roughness of the electrodes to reduce the apparent current density.Herein,molybdenum-and nickel-based composite materials of hierarchical nanostructure were prepared by in situ sulfurization?oxidation?along with spatial constraint strategy of graphene.The composition and structure of composites were characterized using physical measurement methods.Under alkaline conditions,catalytic HER performances of as-prepared composite materials were systematically studied by the electrochemical methods and the relationship between structure and HER performance was also revealed.The findings could provide technical and theoretical supports for the design and manufacture process of new type HER catalysts.The innovative research results are as follows:?1?MoS₂ nanosheets directly growing on Mo mesh were obtained by a one-step hydrothermal process,using Mo mesh as the substrate and molybdenum source and thiourea as sulfurization reagent.The composition and structure of the composites were characterized by XRD,XPS,SEM and TEM.The effects of preparation conditions on the morphologies and structures of composites were revealed.At alkaline media,the cathodic polarization measurements results showed that the electrochemical active surface area?ECSA?of Mo S2@Mo composite was 2 times larger than that of Mo mesh.At a benchmark current density of 10 m A·cm-2,an overpotential of 200 m V was needed for Mo S2@Mo composite along with the Tafel slope of 79 m V·dec-1.The composite also exhibited excellent catalytic stability.The results comfirmed that the Mo S2@Mo composite with high catalytic HER activity could be successfully prepared by in situ sulfurization.?2?Hierarchitectural nanostructure of Mo S2-r GO@Mo composite was successfully synthesized through a one-step hydrothermal method,using molybdenum mesh as the substrate and molybdenum source,conducted by the strategy of in situ sulfurization and spatial constraint of graphene.The composition and structure of the composites were characterized by XRD,XPS,SEM and TEM.Due to the anchoring effect of graphene,Mo S2 nanoparticles were highly dispersed on the graphene surface.Owing to the spatial constraint effect of graphene,the diameter of Mo S2 nanoparticles was smaller and more active edge sites with catalytic activity were exposed.The test results showed that Mo S2-r GO@Mo composite exhibited good electrocatalytic HER activity.At a current density of 10 m A·cm-2,the overpotential of Mo S2-r GO@Mo composite achieved 121 m V,the Tafel slope was 86 m V·dec-1.The composite electrode still exhibited excellent catalytic stability after 1000 CV cycles.The enhanced catalytic HER activity of composite was attributed to the increased ECSA,surface roughness factor and number of the active edge sites.By comparison,the catalytic activity of Mo S2-r GO@Mo was superior to Mo S2@Mo.?3?Nanostructural three-dimension porous Ni3S2@Ni composite was synthesized through a one-step hydrothermal method using foam nickel as the substrate and nickel source.The formation mechanism of composite materials was discussed and the effects of fabricated conditions on the morphologies and structure of composites were illustrated.The electrochemical research results showed that Ni3S2@Ni composite electrode exhibited good electrocatalytic HER performance.At a current density of 10 m A·cm-2,the overpotential of Ni3S2@Ni composite achieved 161 m V,the Tafel slope was 115 m V·dec-1.The composite electrode also exhibited excellent catalytic stability.The catalytic HER activity of composite was significantly improved relative to nickel foam due to the increased ECSA,surface roughness factor and the enhanced TOF.?4?Nanostructural three-dimension porous Ni3S2-r GO@Ni composite was successfully synthesized through a one-step hydrothermal method,using foam nickel as the substrate and nickel source,guided by the strategy of in situ sulfurization and spatial constraint of graphene.The composition and structure of composite were characterized by XRD,XPS and FE-SEM.The formation mechanism of composite was analyzed.The obtained evidences suggested that the formation of unique nanostructural composite with fully exposed active surface was attributed to the self-assembly of Ni3S2 nanosheets on graphene.The test results showed that the overpotential of Ni3S2-r GO@Ni composite achieved 44 m V,and the Tafel slope was 105 m V·dec-1 under a current density of 10 m A·cm-2.The composite also exhibited excellent catalytic stability.The results indicated that the enhanced catalytic HER activity of as-prepared composite was ascribed to the synergistic effect among the increased ECSA,surface roughness factor and number of active sites due to good anchoring and dispersion effect of graphene nanosheets.By comparison,the catalytic activity of Ni3S2-r GO@Ni was superior to Ni3S2@Ni.Therefore,the composite is a promising candidate for non-noble metal catalyst.?5?Nanostructural 3D porous Ni O@Ni composite was synthesized by in situ oxidation method at room temperature,using foam nickel as the substrate and nickel source,potassium persulfate as oxidant.The composition and structure of the composite were characterized by XRD,XPS and FE-SEM.The polarization test results of the as-prepared composite showed that at a current density of 10 m A·cm-2,the overpotential of Ni O@Ni composite achieved 30 m V,the Tafel slope was 108 m V·dec-1.The composite also exhibited excellent catalytic stability after 1000 CV cycles.The good electrocatalytic HER performance resulted from the large ECSA,surface roughness factor and high TOF.Meanwhile,due to the synergistic effect between Ni O and Ni,the catalytic HER activity of composite was significantly improved.Compared with Mo S2-r GO@Mo and Ni3S2-r GO@Ni,Ni O@Ni composite can be prepared more simply and possesses more excellent catalytic HER performance.