电催化还原CO2的功能性离子液体的设计、制备与性能研究

Carbon dioxide is one major cause to green house effects. Effective conversion of carbon dioxide into other useful products has been a challenging problem with increasing concerns around the world. In this project, an ionic liquid with two active sites is going to be used as a catalyst in the electro-reduction of CO2 under benign conditions, in which CO2 will be selectively converted into CO at a low overpotential. The use of ionic liquid as the catalyst will make the whole process more low-carbon, and more efficient. Through investigation of the electro-catalysis behavior and the catalytic reaction,the relationship between the composition and structure of ionic liquid and its impact on the electrochemical catalytic property will be established. Spectroscopy methods, such as in-situ IR, as well as theoretical studies, such as quantum chemistry calculation and cyclic voltammetry simulation, will be utilized to propose the catalysis mechanism and to help understand the catalysis process. Those understanding and knowledge will build strong theoretical foundation to develop more efficient catalysts.

二氧化碳(CO2)是造成温室效应的主要气体，如何有效转化利用CO2，已经成为国际社会普遍关注的问题。本项目拟以具有双催化中心的离子液体作为催化剂,在温和条件下使CO2能在较低过电位下高效的转化为CO，从而整个过程更加低碳、高效。借助于对电催化行为、催化反应的研究，分析催化剂组成和结构与其催化性能的内在联系。利用原位红外等在线光谱手段，结合量化计算和循环伏安模拟，推测催化反应机理，掌握催化过程本质，从而为设计制备更为高效的催化剂提供理论基础。

（1）DMF溶液中研究了季铵阳离子（TAA+）的链长对CO2电还原的影响。线性伏安扫描表明随着TAA+链长增长，CO2电还原的起始电位逐渐负移。密度泛函理论计算揭示了CO2电还原的起始电位由TAA+与电还原生成的CO2.-阴离子自由基之间的静电引力所决定。CO2气体扰动实验证实了CO2还原峰电流则由吸附在电极表面的TAA+的数量所决定；（2）DMF溶液中研究了咪唑阳离子对CO2电还原的影响。密度泛函理论计算表明CO2.-阴离子主要与咪唑阳离子上C2，N1和N3位置上带正电荷的氢原子有静电引力。该静电引力随着N1取代基链长的增长而降低，从而导致CO2电还原的起始电位逐渐负移；（3）使用1-丁基-3-甲基咪唑溴盐（BMIMBr）同时作为支持电解质和助催化剂，电解制备镁盐作主催化剂，开展了CO2和环氧化物反应制备环状碳酸酯的研究。在温和条件下由CO2与一系列环氧化物反应制备得到的环状碳酸酯的产率在48.3～90.7%之间；（4）合成了以二苯基-1-甲基咪唑膦为配体的新型(dpim)2NiCl2配合物。循环伏安结果表明Ni(dpim)2Cl2对CO2还原具有良好的电催化性能，且其电催化过程符合ECE机理。在-1.3 V下恒电位电解得到的还原产物主要为CO，其催化转换频率（TOF）为0.22 s-1。