Modulating Niobium,Tantalum,and Molybdenum-Based Metal Dichalcogenide Nanosheets Structure To Optimize Electrocatalytic Hydrogen Evolution Performance

In recent years,the utilization of traditional petrochemical energy has brought unprecedented challenges such as energy crisis and environmental pollution,and the development of sustainable new energy sources to replace fossil fuels has become a top priority.The design of catalysts plays a pivotal role in sustainable new energy technologies.Hydrogen evolution reaction(HER)is an important way of new energy conversion,and the design of high-performance catalysts is the core issue in the development of sustainable new energy.Platinum(Pt)is considered an ideal electrocatalyst for hydrogen evolution due to its almost no overpotential and very small Tafel slope.However,due to the high price and scarcity of precious metal platinum,scientists have been looking for non-noble metal catalysts that can replace platinum.Transition metal dichalcogenides(TMDs)with two-dimensional layered structures will be the best potential catalysts with practical application prospects and can replace noble metals due to their abundant reserves,low prices,and good catalytic performance.The different construction and arrangement of chalcogenide atoms promote the transition metal dichalcogenide compounds to exhibit diverse phase structures,and different phase states show different electronic structures and properties.Transition metal dichalcogenides with semiconducting properties cannot meet the needs of actual production due to limited catalytic active sites(existing only at the edges)and low electrical conductivity.The design and synthesis of metallic transition metal dichalcogenides is an important strategy to improve current electrocatalysts for hydrogen evolution.This paper focuses on the design and synthesis of niobium,tantalum,and molybdenum-based metal dichalcogenide nanosheets for hydrogen evolution electrocatalytic materials.The electrocatalytic performance of catalytic materials can be optimized by modulating the morphology,electronic structure,metal phase structure and building heterojunction interface of catalytic materials.At the same time,with the aid of the first principle simulation calculation of density functional theory,this paper discusses the structure-activity relationship between element doping,heterogeneous structure and catalytic performance,explores the catalytic reaction mechanism,and comprehensively understands the essence and internal factors of catalytic mechanism.This work will open up a new way for the design and performance optimization of non-noble metal catalysts,and promote the rapid development of sustainable new energy;at the same time,it will contribute to further enrich and deepen the understanding of nano-catalysis science.The specific research contents are as follows:1.Improved the hot injection synthesis process,P,Se co-doped NbS₂ 3D nanosheets were successfully prepared,electrocatalytic hydrogen evolution performance test shows that:the co-doped 3D nanosheets have the best HER activity under acidic conditions.Its overpotential at 10 mA cm^-2 current density is 352 mV,which is 165 mV lower than that of undoped NbS₂ 3D nanosheets and 206 mV lower than that of undoped NbS₂ 2D nanosheets,and it has the smallest Tafel slope(116.7 mV dec^-1).The structural characterization and experimental results show that the co-doping of P and Se elements and the advantages of the three-dimensional structure jointly promote the improvement of the hydrogen evolution performance of NbS₂.Density functional theory calculations further confirm:the co-doping of P and Se stimulates the activity of original inert niobium atom,reduces the free energy of hydrogen adsorption on niobium atomic sites,and promotes S and Nbdouble active sites to participate in the catalytic reaction.Meanwhile,Se doping plays an important role in improving the stability of NbS₂.2.Developed the hot injection method,the 1T-2H heterogeneous TaS₂ nanosheets with tunable phase structure were successfully prepared,and three different stacking forms were constructed and contained structural defects.The electrocatalytic hydrogen evolution performance test shows that:under acidic conditions,the electrocatalytic activity of ultrathin 1T-2H heterogeneous TaS₂ nanosheets is the best.When the current density is 10 mA cm^-2,the overpotential is 280 mV,and the current density has no obvious change after 10,000 cycles,showing good electrocatalytic stability.The excellent electrocatalytic activity can be attributed to the existence of a large number of highly active 2H phases and structural defects in the ultrathin 1T-2H heterogeneous TaS₂ nanosheets.Theoretical calculation studies further confirm that the 2H phase has a hydrogen adsorption free energy closer to zero than the 1T phase,and the combined effect of the 2H phase and the defect structure optimizes the hydrogen adsorption free energy on the 1T-TaS₂ basal plane,thereby effectively promoting the HER activity.3.Designed a step-by-step liquid phase synthesis method,MoSe₂nanosheets/RuSe₂ nanoparticles heterostructures were successfully prepared.The electrocatalytic hydrogen evolution performance test shows that:it has the lowest overpotential(48 mV)at a current density of 10 mA cm^-2 and the smallest Tafel slope(72.6 mV dec^-1).XPS analysis shows that there is obvious electron interaction and electron transfer between MoSe₂ and RuSe₂.The heterostructure modulates the intrinsic electronic structure of each component,and then the MoSe₂ nanosheet/RuSe₂nanoparticle heterostructures show the best HER electrocatalytic performance.