Design And Hydrogen Evolution Performance Of Molybdenum Disulfide Based Electrocatalysts

The consumption of fossil fuels with limited reserves has caused serious ene rgy def icit and enviro nmental probl ems.Theref ore,the dev elopment of enviro nment-frie ndly new ene rgy sour ces with wi de raw materials has gradually beco me the focus of research.Hydrogen is of great co ncern becau se of its high energy dens ity and the fact that no pollu tants are rele ased d uring combustion.The production of hydrogen from water by electro-catalysis is more environmentally frien dly than the trad itional b y-product of hydrogen refining.However,most of the catalysts used for hydrolysis are precious metals.In order to reduce the cost of hydrogen production,transition metal compounds have been used as inexpensive substitutes for noble metal catalysts.Over the years,a series of encouraging advances have been made.In this paper,a series of self-supporting molybdenum disulfide based polymorphic electrocatalysts were deposited on conductive substrates and good experimental results were obtained.（1）A two-step hydrothermal method is proposed to prepare 3D reticulated Ni₃（VO₄）₂ultra-thin nanosheets on the surface of Mo S₂ nanosheets.Unlike traditional two-dimensional composites,Ni₃（VO₄）₂ ultrathin nanosheets intersect with Mo S₂ grown on carbon cloth to fo rm a uni que thr ee-dimen sional netw ork（Ni₃（VO₄）₂/Mo S₂@CFC）.The coupling effect between Ni₃（VO₄）₂ nanosheets and Mo S₂ enlarges the catalytic active region and enhances the intrinsic activity of HER.Ni₃（VO₄）₂/Mo S₂@CFC exhibits high activity at industrial electrolysis temperature（75°C）,overp otential 77 m V(10 m A cm^-2)and Taf el slope 65 m V dec^-1.And the material exhibited good catalytic stability in 0.5 M H₂SO₄.This work provides a heterogeneous coupling scheme for the construction of new non-noble metal hydrogen evolution catalysts.（2）The development of electrocatalysts for hydrogen evolution with rich electrocatalytic sites and high intrinsic activity is a major challenge for current water electrolysis technologies.An efficient sea urchin electrocatalyst(Mo₄O₁₁-Mo S₂-VO₂)was synthesized by hydrothermal deposition and annealing.The overpotential of HER was only 43 m V(10 m A cm^-2)and the slope of Tafel was only 37m V dec-¹ at 0.5M H₂SO₄,which was better than most non-noble metal electrocatalysts deposited on carbon cloth.It is worth mentioning that the multi-echelon structure promotes electron redistribution and provides more catalytic sites.This design strategy provides an idea for the prepa ration of non-nob le me tal electroca talysts in the future.（3）Producing inexpensive and efficient bifunctional electrocatalysts to replace precious metal materials and to promote the production and transformation of sustainable energy is a major challenge.On this basis,based on the theory of intermediate adsorption and d band center,we demonstrate the Ni₃S₂-Mo-Fe nanorod array of Mo-S-Fe engineering as an inexpensive and efficient hydrolysis catalyst.High-quality nano-arrays ensure adequate contact between the surface of the catalyst and the electrolyte,increasing the number of sites involved in the reaction.Various characterizations show that the introduction of Mo and Fe in Ni₃S₂ not only increases the number of active sites,but also increases the intrinsic conductivity of the catalyst.Theoretical calculations show that the introduction of Fe and Mo atoms can adjust the adsorption energy of the catalyst on the hydrolysis intermediates and inc rease the d ban d ce nter.The resu lts show that Ni₃S₂-Mo-Fe has good electrochemical properties.In 1M KOH,the OER process at 10 m A cm^-2 current density needs only 178 m V overpotential.In addition,the current density of 10 m A cm^-2 can obtained at 1.62 V,and the catalytic activity of the Ni₃S₂-Mo-Fe two-electrode cell remains good after 24 h of continuous full hydrolysis.It provides a feasible and promising strategy for preparing inexpensive electrocatalysts for hydrogen production from water.