Design,Regulation,and Performance Of Nickel-Molybdenum-Based Sulfide On Hierarchical Carbon Framework For Electrocatalytic Hydrogen Evolution

Hydrogen generation by electrocatalysis water splitting is considered as one of the most promising techniques for the conversion and storage of renewable energy.In order to overcome the slow kinetic process of hydrogen evolution and improve the energy conversion efficiency,it is very important to design highly efficient,low-cost,and stable catalysts.Owing to their low cost and similarities to the active center of hydrogenase,transition metal sulfides,especially molybdenum disulfide（Mo S₂）,have been considered to be promising substitutes to Pt-based materials,but the inherently low conductivity,finite active edge sites due to the thermodynamically stable basal plane,and the self-stacking and agglomeration properties of molybdenum disulfide still impede the hydrogen evolution reaction activity.Moreover,the transport of electrolyte reactants and hydrogen bubbles is also an important factor affecting the rate of electrocatalytic hydrogen evolution.Therefore,it is also crucial to optimize the morphology and structure of electrodes.In addition,the conventional electrode fabrication procedure by drop-casting also has the problems of buried active material and poor mechanical stability.Based on these,this thesis has optimized the Mo S₂-based catalyst from four aspects:improving the intrinsic activity of the catalyst,increasing the number of active sites,facilitating the mass transfer,and improving the overall conductivity.Firstly,we prepared a manganese-doped Mo S₂ ultrathin nanosheet vertically anchoring on a fin-tube-like hierarchical carbon skeleton composite electrode to achieve the synergistic optimization of intrinsic activity and electrode architecture.The superhydrophilic and superaerophobic electrode with conductive carbon nanoarray structure can accelerate the mass transport（gas bubbles and electrolyte）and electron transfer processes.The ultra-small size of the nanosheet can greatly expose the active sites.In addition,theoretical calculation reveals that all the hydrogen adsorption free energies of basal planes,S-edge,and Mo-edge for doped Mo S₂ have decreased.Moreover,the electronic structure of the Mn-doped Mo S₂monolayer shows the absence of band gap,indicating improved inherent conductivity.This finely crafted self-supported binder-free electrode with integrated architecture shows a low overpotential of 130 m V at-10 m A/cm²,a Tafel slope as low as 44 m V/dec,and excellent durability even at a high cathodic current density of 200 m A/cm² in 0.5 M H₂SO₄.Secondly,on the basis of the slow kinetics of hydrogen evolution for Mo S₂ under alkaline condition,and considering that the Volmer step of hydrogen evolution in alkaline electrocatalysis involves the adsorption and cleavage of water molecules,this thesis prepared interface/defect-rich Mo S₂/Ni₃S₂ heterostructure for alkaline hydrogen evolution by introducing water decomposition promoter Ni₃S₂ at edge of Mo S₂ with excellent hydrogen adsorption characteristics This work directly vulcanized the solid Ni Mo O₄ nanosheets at a low temperature to realize the construction of heterogeneous interface with synergistic effect between the hybrid two component system.The resulting cobalt-doped Mo S₂/Ni₃S₂ heterogeneous nanosheet anchoring on hierarchical carbon catalytic electrode shows a low overpotential of 89 m V at-10 m A/cm² in 1 M KOH,a Tafel slope as low as 60 m V/dec,and can run at-100 m A/cm² for at least 50 hours without obvious voltage change.The multi-scale optimization strategy from intrinsic activity to electrode morphology and structure,from atomic scale to micro-nano scale,may provide references for the design of commercially feasible electrocatalysts.