| Development of clean and renewable resources is of great significance due to the increasingly serious problems of energy crisis and environmental pollution.Hydrogen production by electrolysis of water has attracted widespread attention because of its green and high efficiency.Pt-based catalysts are limited by high cost and low reserves and cannot be used in large-scale production.Therefore,it is necessary to develop efficient and cheap electrocatalysts to replace Pt.Earth-rich Mo S2 own the great free energy of hydrogen adsorption at the edge sites which is similar to Pt,making it one of the alternative materials for Pt-based catalysts.However,the layered structure leads to poor charge transport ability in interlayers,and only the edge sites are active.A large number of basal planes exhibit hydrogen evolution sluggishness,which severely limits the improvement of their electrocatalytic performance.At present,there are many ways to enhance the hydrogen evolution performance,and the nanosheet structure fabricated by the hydrothermal over conductive substrates can help to fully expose the active sites and improve the conductivity.However,many basal planes are still catalytically inert,and the development of Mo S2 under alkaline conditions is still challenging.To this end,this study mainly focuses on the faburication of S-vacancy and the hydrogen evolution reaction under alkaline.The main contents are as follows:(1)The Ru-doped Mo S2 and Co S2 composite structure was successfully synthesized by modifying the self-assembled Mo S2 on CC by directly introducing Ru and Co precursor during the reaction.Both Ru and Co S2 can excite a certain amount of S-vacancy in Mo S2,and more S vacancies are finally excited in Mo S2 to activate the inert basal plane through the synergy between them.At the same time,combined with theoretical analysis and experimental verification,a feasible catalytic mechanism is proposed,the introduction of Ru can introduce-OH at the S-vacancy,and form a strong H bond with H2 O in the electrolyte during the reaction process.Thus,facilitating the reactants to reach the catalyst surface can accelerate the rate of hydrogen evolution.What’s more,the synergistic effect between water dissociation by Ru and vacancy active center is also beneficial to the generation of H2.This catalyst exhibits a hydrogen evolution overpotential of-73 m V at a current density of-10 m A cm-2(1 M KOH).In addition,the stability of the catalyst is still good after 1000 cycles and 10 h chronoamperometry.(2)On the basis of the above experiments,the amount of Ru and Co precursors in the same synthesis process is changed.The results show that the excitation effect of vacancies is weaker under the effect of Ru or Co S2.The concentration of S-vacancy(Cs-vacancy)is more sensitive to the amount of precursors when Ru and Co precursors are used simultaneously and the Cs-vacancy is larger.A simple change in the amount of the precursor can finally achieve effective regulation of the Cs-vacancy in the Mo S2 basal plane.There is an obvious balance between the Cs-vacancy and charge transport in this catalyst: An excessively high Cs-vacancy leads to a larger charge transport resistance(Rct).Therefore,an appropriate Cs-vacancy(17.1%)can effectively activate the inert basal plane of Mo S2 to achieve efficient hydrogen evolution.The results of TOF calculation reveal that the appropriate Cs-vacancy also has the best intrinsic activity.At the current density of-100 m A cm-2,the hydrogen evolution overpotential is only-170 mV. |
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