【作者】 杨涛；

【导师】 李青； 迟力峰； 朱嘉；

【作者基本信息】 苏州大学 ， 物理学， 2019， 硕士

【摘要】 二氧化碳(CO2)电化学催化还原为甲酸、一氧化碳以及甲烷等增值产物是实现CO2资源循环利用的有效途径。二氧化碳一般涉及多个质子-电子对转移才能被还原为甲烷等增值产物,反应历程和机理相当复杂。电化学热力学分析方法在研究催化反应机理和预测催化剂催化活性方面得到了广泛的认可,本文基于电化学热力学方法并结合密度泛函理论计算系统地研究了金属配合物M-BHT(M=Cu,Co)与氮、磷-共掺杂富勒烯结构作为CO2还原电催化剂的催化特性。本文主要内容和结果为:1.论文研究思路(1)通过计算CO2还原为特定产物(如CH4)的可能反应中间体(*CO2、*COOH和*CO等)在催化剂表面的自由能,以及反应所涉及的可能的基元反应的自由能变化得到整个反应的最低能量路径(反应机理)的自由能图;(2)根据最低能量路径得到反应的速控步骤(活性决定步骤)所涉及的基元反应的自由能变化得到反应的起始电位;(3)结合起始电位的大小分析不同催化剂的催化性能;(4)结合电子结构计算结果初步分析催化剂催化活性与其电子结构的相互关系。2.Cu-BHT作为CO2还原电催化剂的研究构建了单层和双层(1×1)Cu-BHT(001)表面结构并研究了其将CO2还原为CH4的电催化特性。研究结果表明:CO2在单层与双层Cu-BHT表面上还原为CH4的反应机理和催化活性位点相同;单层Cu-BHT的催化活性高于双层Cu-BHT,理论起始电位分别为-0.76 V和-1.02 V;反应的速控步骤为*CO2+H+e-→*COOH;3.Co-BHT作为CO2还原电催化剂的研究构建了单层和双层(1×1)Co-BHT(001)表面结构并研究了其将CO2还原为CH4的电催化特性。研究结果表明:CO2在单层与双层Cu-BHT表面上还原为CH4的反应机理和催化活性位点相同;理论起始电位分别为-0.66V和-0.58 V,即双层Co-BHT催化活性高于单层;4.M-BHT(M=Cu,Co)作为CO2还原电催化剂的研究构建了(3×1)Cu-BHT(001)表面结构并研究了其将CO2还原为CH4和HCOOH的电催化特性并与(1×1)Co-BHT(001)催化特性进行对比。研究结果表明:双层Co-BHT将CO2还原为CH4的催化活性高于双层Cu-BHT;Co-BHT将CO2还原为HCOOH的催化活性高于Cu-BHT。5.氮、磷共掺杂富勒烯结构作为CO2还原电催化剂的研究构建了不同类型氮掺杂富勒烯结构与氮、磷共掺杂富勒烯结构并研究了其将CO2还原为CO的催化特性。结果表明:吡啶氮和磷共掺杂富勒烯结构的催化活性最好(理论起始电位为-0.27 V),速控步骤为*CO解吸附过程。中间体*COOH的吸附能与形成*COOH所需的热力学能垒成良好的线性关系。更多还原

【Abstract】 One of the most effective ways to achieve CO2 recycling is the electrochemical catalytic reduction of CO2 to value-added products such as formic acid,CO,and CH4.In general,the complexity of the charge transfer process occurs during carbon dioxide reduction reactions(CO2RR).The electrochemical thermodynamic analysis method has been widely used for interpreting the underlying catalytic mechanism and prediction of metal complexes M-BHT(M=Cu,Co)and N,P-co-doped fullerene for CO2RR by density functional theory calculation and electrochemical thermodynamic analysis method combined with computational hydrogen electrode(CHE)model.The main contents and results are as follows:1.Research process in this thesis(1)First,the free energies of all possible reaction intermediates(*COOH,*CO,*CHO,etc.)of CO2 reduction to special products such as CH4 were calculated.Second,the free energy changes of all possible elementary reaction steps were calculated.Finally,the free energy diagram of the lowest energy pathway(reaction mechanism)of the reaction was obtained.(2)Determined the rate-limiting step and calculated onset potential of the reaction based on the free energy diagram(3)According to the value of onset potential,compared the catalytic activities of different catalyst(4)The origin of catalytic activity was analyzed based on the results of the electronic structure of the catalysts.2.Theoretical investigations of the electroreduction of the CO2 on the Cu-BHTMonolayer and bilayer(1x1)Cu-BHT(001)were constructed and their electrocatalytic properties of CO2 reduction to CH4 were investigated.The results are as follows:the reaction mechanism and activity site of CO2 reduction to CH4 on monolayer Cu-BHT(001)are the same as those on the bilayer Cu-BHT(001).The catalytic activity of monolayer Cu-BHT as electrocatalysts for CO2 reduction to CH4 is higher than that of bilayer Cu-BHT.The theoretical onset potentials are-0.76 V and-1.02 V,respectively.The rate-limiting step of the reaction is CO2+H++e-→*COOH.3.Theoretical investigations of the electroreduction of the CO2 on the Co-BHTMonolayer and bilayer(1×1)Co-BHT(001)were constructed and their electrocatalytic properties of CO2 reduction to CH4 were investigated.The results are as follows:the reaction mechanism and activity site of CO2 reduction to CH4 on monolayer Co-BHT(001)are the same as those on the bilayer Co-BHT(001).The catalytic activity of bilayer Co-BHT for CO2 reduction to CH4 is higher than that of monolayer Co-BHT.The theoretical onset potentials are-0.66 V and-0.58 V,respectively.4.Theoretical investigations of the electroreduction of the CO2 on the M-BHTThe(3×1)Cu-BHT(001)was constructed and the electrocatalytic properties of CO2 reduction to CH4 and HCOOH were studied and compared with the catalytic properties of(1×1)Co-BHT(001).The results are as follows:the catalytic activity of bilayer CoBHT toward the CO2 reduction to CH4 is better than that of bilayer Cu-BHT.The catalytic activity of Co-BHT toward CO2 reduction to HCOOH is better than that of Cu-BHT.5.N,P-doped fullerene electrocatalysts for carbon dioxide reduction reactionDifferent types of N-doped fullerene(C60)and N,P co-doped fullerene were constructed and their catalytic properties for CO2 reduction to CO were studied.The results are as follows:the pyridinic N and P co-doped fullerene exhibits the best activity(theoretical onset potential:-0.27 V)for CO2 reduction to CO,in which the reaction ratelimiting step is the desorption of*CO.The adsorption energy of*COOH has a good linear relationship with the thermodynamic energy barrier for forming*COOH.更多还原