Ultrafine Carbon Fiber Limited Domain Regulation Of Noble Metal@MoS₂ Core-shell Nanostructure And Its Electrocatalytic Behavior

In order to solve the environmental and energy problems brought by fossil fuels,scientists are striving to develop efficient and clean sustainable energy.Hydrogen has received extensive attention as an environmentally friendly energy source,and electrolyzed water is the cleanest and most efficient technology among many hydrogen production methods.Electrolyzed water essentially requires a catalyst to improve its slow hydrogen evolution kinetics.Pt-based catalysts are currently the most ideal electrolyzed water catalysts,but their high price and scarcity make scientists discouraged.Therefore,it is urgent to find a non-precious metal catalyst which can compete with the performance of Pt-based catalysts to promote the popularization and application of electrolyzed water.With the rapid development of nanoscience and technology,zero-dimensional nanoparticles and two-dimensional nanomaterials are widely used in the field of nanocatalysis.As a material with a graphene-like layered structure,MoS₂ has been widely concerned by scientists and it has been confirmed that its edge is its catalytic active center.In this paper,a core-shell nanocatalyst formed by self-assembly of zero-dimensional noble metal nanoparticles and two-dimensional MoS₂nanosheets was prepared by combining the mature electrospinning process with sulfur vapor-assisted chemical vapor deposition,and applied to electrolyzed water to produce hydrogen,and to explore the core between shell nanostructures and electrolyzed water of structure-activity relationship.The main contents are as follows:（1）The Au-Mo-PAN precursor fiber membrane was prepared by electrospinning process,and the Au-MoS₂ core-shell polyhedral nanomaterial was prepared by high temperature carbonization and sulfur vapor assisted chemical vapor deposition.Using a three-electrode system,the hydrogen evolution overpotential was only 92 mV and the Tafel slope was only 102 mV dec-1 with 0.5 M H₂SO₄ electrolyte,and it had excellent stability.The polyhedral core-shell structure exposes more active sites,and the synergistic catalysis between the core and the shell significantly increases the activity of the catalyst.The strong coupling between carbon nanofibers（CNFs）and the core shell gives the catalyst excellent stability.（2）Synthesis and regulation of Pd₁₆S₇/MoS₂/CNFs droplet-shaped core-shell nanostructures using carbon nanofibers（CNFs）as nanoreactors.The Pd₁₆S₇/MoS₂/CNFs core-shell self-supporting electrode has the hydrogen evolution overpotential of only 83 mV in a 0.5 M H₂SO₄ electrolyte,and the corresponding Tafel value is only 113 mV dec^-1.It also has excellent stability.The conductor Pd₁₆S₇ effectively regulates the surface electron morphology of the semiconductor MoS₂ and the self-assembled core-shell nano-interface exposes more active sites,which significantly enhances the hydrogen evolution activity.The contact angle test confirmed that the core-shell nanocrystals have excellent hydrophobic properties,accelerate the gas desorption process,weaken the destructive force to the catalyst structure during gas desorption,and improve the stability of the catalyst.（3）Uniform 5 nm Pt-Mo alloy nanocrystals were prepared by electrospinning technique and high temperature carbonization process.The Mo₃Pt/CNFs self-supporting electrode has a hydrogen evolution potential of only 73 mV in a 0.5 M H₂SO₄ electrolyte,and Tafel has only108 mV dec^-1.And has excellent stability.Small-sized Pt-Mo alloy nanocrystals exposed more active sites and excellent synergy between Pt and Mo,which significantly improved the hydrogen evolution activity of Mo₃Pt/CNFs catalysts.The strong coupling between the CNFs and the alloy gives the catalyst excellent stability.