Preparation Of MOF-Derived Cu-Doped Ruthenium Chalcogenide Electrocatalysts For Hydrogen Evolution Reaction

Due to the large-scale use of traditional fossil fuels,environmental problems such as global warming caused by energy crisis and carbon emissions are becoming more and more serious.The exploration and development of new clean and sustainable energy and related energy conversion technologies have become the focus of human survival and world development.Hydrogen energy has the advantages of high energy density,rich sources and zero emission after combustion,so it is considered to be one of the most promising alternatives to fossil fuels in the future.Among all kinds of hydrogen production technologies,hydrogen production from electrolytic water has become one of the most promising hydrogen production technologies because of its advantages such as large-scale production of high purity hydrogen,no carbon emission and sustainability,which has been widely concerned by academia and industry.At present,the precious metal platinum(Pt)has the best intrinsic electrocatalytic activity for hydrogen evolution reaction(HER),especially under acidic conditions,it is recognized as the benchmark electrocatalyst for HER.However,the reserves of platinum are scarce,the cost is high,and platinum has poor activity under alkaline conditions,which greatly hinder its popularization and application in electrolytic aquatic hydrogen production technology.Therefore,the development of new and efficient HER electrocatalysts has become an urgent task to popularize the technology of hydrogen production by hydrolysis,which has important practical significance for promoting the sustainable development of hydrogen energy industry.Ruthenium(Ru)has lower cost than Pt,but it has similar hydrogen adsorption capacity and stronger corrosion resistance to Pt.More importantly,it has the ability to promote the dissociation of water,which is beneficial to the electrocatalysis of HER under alkaline conditions.In addition,metal-organic framework(MOF)materials have unique advantages such as porosity and large specific surface area,and are easy to modify after synthesis,which is an ideal choice for the construction of excellent electrocatalysts.In this paper,Cu-doped ruthenium chalcogenide electrocatalysts were in-situ synthesized for hydrogen evolution under alkaline conditions using polyhedral Cu-based MOF(Cu-BTC,BTC=1,3,5-Benzenetricarboxylic acid)as the precursor via cation exchange reaction and subsequent heat treatment/vapor deposition techniques.These specific works are as follows:(1)Bimetallic MOF of RuCu-BTC was synthesized by cation exchange reaction using polyhedral Cu-BTC as a precursor,and then Cu doped RuS2/Ru heterostructure(Cu-RuS2/Ru)with hollow polyhedron morphology was successfully synthesized by pyrolysis in air and further sulfuration via vapor deposition method in argon atmosphere.The microstructure and formation process of the target catalyst were analyzed by scanning electron microscope(SEM),transmission electron microscope(TEM),X-ray energy dispersion spectroscopy(EDS),X-ray diffractometer(XRD),X-ray photoelectron spectroscopy(XPS)and other material characterization techniques.The electrocatalytic hydrogen evolution performance and stability of the catalysts were tested by linear sweep voltammetry(LSV),cyclic voltammetry(CV),electrochemical impedance spectroscopy(EIS)and chronopotentiometry(E-t).Benefitting from Cu heteroatom doping of RuS2,heterointerface design and three-dimensional hollow polyhedron morphology,the Cu-RuS2/Ru catalyst shows good HER electrocatalytic activity.In 1 M KOH aqueous solution,the Cu-RuS2/Ru catalyst exhibits a low overpotential of 67 mV at a current density of 10 mA cm-2 with a Tafel slope of 70 mV dec-1 and significantly improved HER kinetics.Importantly,Cu-RuS2/Ru only needs an overpotential of 169 mV to drive a large current density of 200 mA cm-2 with good stability,which is superior to commercial Pt/C catalysts.In addition,density functional theory calculations indicate that the incorporation of Cu heteroatoms can not only decrease the energy barrier for water dissociation of RuS2 but also optimize its hydrogen adsorption.(2)Bimetallic MOF of RuCu-BTC was synthesized by cation exchange reaction using polyhedral Cu-BTC as a precursor,and then carbon layer modified Cu doped RuSe2 composite catalyst(Cu-RuSe2@C)with polyhedral structure was successfully synthesized by one-step selenization via vapor deposition method.The microstructure and composition of the prepared electrocatalyst were characterized by SEM,TEM,XRD,XPS and Raman spectroscopy,and the electrocatalytic performance of alkaline hydrogen evolution was studied by LSV,CV,EIS and E-t.Benefitting from the doping of Cu heteroatom in RuSe2,carbon layer modification and three-dimensional polyhedral morphology,Cu-RuSe2@C catalyst shows excellent HER electrocatalytic activity.In 1 M KOH aqueous solution,Cu-RuSe2@C needs only 45 mV overpotential to drive a current density of 10 mA cm-2,and the slope of Tafel is only 43 mV dec-1.Cu-RuSe2@C catalyst exhibits superior HER electrocatalytic performance with good stability,which is better than that of commercial Pt/C catalyst.