| Hydrogen energy?H2?,as a non-toxic,high calorific value,zero pollution of combustion products,sufficient source of sustainable and renewable energy,is a promising candidate for substituting traditional fossil fuels,to address the cumulatively severe greenhouse effect,energy crisis and environmental pollution issues.The electrolysis of water for hydrogen production is an effective path to obtain hydrogen energy.However,the commercial catalysts for hydrogen evolution are still the precious-metal Pt-based catalysts at present,which is limited to implement a wide range of applications due to the scarcity,high cost and non-renewability of precious metals.Therefore,the design and exploitation of cheap and efficient non-noble metal electro-catalysts to achieve large-scale applications has always been a problem that researchers have to solve urgently.Molybdenum disulfide?Mo S2?,as a typical transition metal disulfide compound?TMDs?,has attracted researchers'attention in recent years with its large active surface area,high controllability,abundant reserves,and low price.In this paper,based on the catalytic mechanism of Mo S2,a series of studies have been investigated to improve its catalytic performance for HER by utilizing distinct strategies.The specific research contents are as follows:?1?Using a simple one-step hydrothermal method,Mo S2 nanostructures with the different morphologies are synthesized:one is independent,non-stacked spherical nanoflowers?SNF-Mo S2?,another is defect-rich random nanosheets?RNS-Mo S2?,by regulating the ratio of molybdenum source and sulfur source.Raman and X-ray photoelectron spectroscopy?XPS?analysis indicate that the as-prepared Mo S2 samples are mixed-phase nanomaterials containing 1T metal phase and 2H semiconductor phase.Both of samples exhibit better performance of electrocatalytic HER and supercapacitor,which because the part of 1T phase can significantly improve the conductivity of the material.In addition,to analyze the effect of conductivity on the catalysis of these two types of nanostructures and further improve the performance of the catalyst,we introduced a small amount of carbon black into the catalyst through simple physical doping.The SNF-Mo S2/C and RNS-Mo S2/C samples have an overpotential of 220 m V and 203 m V at a current density of 10 m A cm-2,and Tafel slopes are 65.7 m V dec-1 and53.7 m V dec-1,respectively.And after 5000 cycles of cyclic voltammetry?CV?,the electro-catalytic performance is basically not decayed,indicating both samples have excellent cycle stability.Besides,the discharge specific capacitances of SNF-Mo S2 and RNS-Mo S2 are 165.1 F g-1and 242.3 F g-1at a current density of 1A g-1,respectively.?2?In order to capture the problems of self-aggregation and poor conductivity of Mo S2,we used Co P material derived from ZIF-67 as the substrate,and successfully accomplished the composite of Mo S2 nanosheets on the surface of the Co P substrate in situ by hydrothermal method.And a series of Co P@Mo S2 composite materials with hollow and core-shell structure were prepared.The composite material combines the advantages of the two components,including the good conductivity of the Co P substrate and the large active surface area of Mo S2.The results of XPS analysis indicate that the electron transfer from the Co P substrate to Mo S2 occurs between the two components,which possesses a regulatory effect for the catalytic site activity of Mo S2on the surface.The electro-catalytic test results reveal that the composite material exhibits excellent electro-catalytic performance for HER in acidic environment,especially the Co P@Mo S2-75 sample:its overpotential is only 119 m V at a current density of 10 m A cm-2,the Tafel slope is 49 m V dec-1,and it possesses a larger electric double layer capacitance(Cdl)of 10.28 m F cm-2.This synergy effect between Co P substrate and Mo S2 has made important contributions to regulating the activity of catalytic sites of Mo S2 and improving the catalytic performance of materials. |
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