Preparation Of Two-dimensional Bimetallic Compounds And Electrocatalytic Conversion Of Energy Small-molecules

Electrocatalytic conversion of energy small-molecules using clean electricity to convert small-molecules such as water,carbon dioxide into chemicals,is a green technology to alleviate the environmental pollution and the shortage of fossil energy.The design and synthesis of efficient electrocatalysts for the conversion of energy small-molecules determine the further development.To achieve this goal,the electrocatalysts need to realize the efficient water oxidation reaction at a low potential on anodes and obtain the efficient conversion of carbon dioxide on cathodes.Recently,two-dimensional materials provide an opportunity for efficient conversion of energy small-molecules because of their high exposure of the atom and clear crystal face.Metal atoms are the main active sites in two-dimensional materials for electrocatalytic conversion of energy small-molecules.However,energy small-molecules are a highly stable molecules.The simple electronic structures of monometallic compounds are the bottlenecks for efficient chemisorption of energy small-molecules during the electrocatalytic process,which implies that the monometallic compounds cannot meet the practical needs for efficient conversion of energy small-molecules.Currently,constructing bimetallic compounds are regareded as a potential path for optimizing the adsorption ability of active sites.Based on these,this paper starts from the controllable preparation of two-dimensional bimetallic compounds,then explores the optimizing mechanism of bimetallic effect on the chemisorption of energy small-molecules during electrocatalytic process,so as to realize the efficient electrocatalytic conversion of energy small-molecules.The main research contents list as follows:（1）Producing hydrogen from water electrolysis is limited by the high overpotential of water oxidation reaction in the anodes.Concerted efforts to promote the desorption of intermediates generated by water oxidation would reduce the overpotential.Herein,N,S co-doped carbon layer encapsulated Fe-Co₉S₈ nanosheets were prepared by rapid thermal treatment.Benefited from the Fe doping,d band centers of Co₉S₈ was declined,leading to weakened the adsorption of oxygen intermediates.The catalysts delivers a potential of 1.50V at a current density of 10 m A cm^-2,and its water oxidation activity is superior to that of the commercial Ru O₂ at the higher potential than 1.52 V.（2）Replacing the water oxidation reaction with thermodynamically favorable ethanol oxidation reaction,is a practicable alternative to reduce the potential for producing hydrogen from water electrolysis.However,due to their multiple chemical bond and large size,hindering the chemisorption on the active sites,ethanol conversion suffer from low catalytic efficiency.Based on this,multi-porous Co Ni hydroxide nanosheets were fabricated by the ligand exchange between alkali and organic ligand.The charge transfer between Co²⁺and Ni²⁺is the key to enhancing the chemisorption of ethanol,realizing the current density of10 m A cm^-2 for the ethanol electrooxidation at a potential of 1.39 V.（3）Except that a low potential for water oxidation reaction on anodes is essential,improving the efficiency of carbon dioxide reduction reaction on cathodes is another key in realizing efficient conversion of carbon dioxide.Limited by the intermediates with insufficient selective adsorption on the catalysts,carbon dioxide conversion still suffer from low catalytic efficiency at a wide potential range to produce formate.Based on this,Cu₂Sn S₃nanosheets were obtained by hydrothermal method.During carbon dioxide reduction reaction,Cu₂Sn S₃ has undergone a structural reconstruction,resulting in the formation of Cu S/Cu₂O@Sn O₂.The delocalized Sn⁴⁺were stablized by the charge transfer in the heterojunction interface,leading to the Faradaic efficiency more than 83.4%for formate formation in a wide potential range from-0.6 V to-1.1 V.In summary,the adsorption capacity of two-dimensional materials for energy small-molecules can be optimized through bimetallic effect.The main functions as follows:By using metal hetero-atoms doping to shift d band centers of the host materials,the adsorption capacity was weakened;However,the coupling of two metal hetero-atoms generate the charge transfer,enhancing the adsorption capacity.