【作者】 吴超；

【导师】 张鹏； 章福祥；

【作者基本信息】 郑州大学 ， 材料工程（专业学位）， 2022， 硕士

【摘要】 目前全球能源结构还是以化石能源为主,非化石能源也在稳步增长,化石能源产生的CO₂引发了一系列能源和环境问题。与此同时,电能过剩不易存储也成为亟待解决的问题。电催化二氧化碳还原反应（CO₂RR）可以将CO₂转化为具有高附加值燃料和化学品,产品也可以作为能量的载体分子来存储电能,人工实现碳循环的闭合,不仅可以缓解“温室效应”,也有利于“双碳”目标的达成。铜基催化剂用于CO₂RR制多碳产物(C₂₊)的研究是极具研究潜力和挑战的课题,铜是目前唯一能高效将CO₂电还原为多碳烯烃或醇的金属,但其还原产物极其复杂、析氢副反应严重、C₂₊法拉第效率低下、活性不高以及稳定性较差。寻找及研究产生C₂₊的真正催化活性位点及生成机制对于此研究方向尤为重要,这也是控制其选择性的关键。提高C₂₊的选择性需要调控^（9）CO的化学行为,使其向^（9）C₂的方向发展。Cu的纳米结构,电子结构以及化学环境与关键中间体的吸附活化以及转化活化能息息相关,本论文研究如下:（1）通过沉淀法合成了铜催化剂的预催化剂,首先研究了合成过程中不同前驱物电化学重构产生的铜用于CO₂RR,Cu O衍生的铜比表面积大,具有复杂的晶界网络（111）/（100）,因而表现出高的C₂₊选择性（78%）和分电流密度(663 m A cm^-2)。通过调控氧化物衍生铜的Cu（111）与Cu（100）的晶面比例研究了晶面对于C₂₊选择性的影响,发现Cu（111）和（100）晶面协同催化促进了不同构型的^（9）CO的覆盖度以及后续加氢、C-C耦合反应进程,进而提高了C₂₊的选择性。（2）通过热还原以及高温氢气还原的策略制备了一种金铜复合材料,10 nm左右的Au颗粒负载在铜载体上。Au给Cu提供了一个表面富^（9）CO中间体的化学环境,提高了Cu进行碳碳耦联的效率。相比于纯铜材料,Au/Cu-H300复合材料表现出更优的CO₂RR性能,显著提高了正丙醇（n-Pr OH）的法拉第效率。Au与Cu协同促进了^（9）C₂的产生以及^（9）C₂与^（9）C₁的耦联,通过调节Au的负载量发现n-Pr OH的法拉第效率能达到14%,是纯铜的4倍多。本章设计的串联催化剂为制备高C3产物选择性的铜基催化剂提供了一种思路。更多还原

【Abstract】 At present,the global energy structure is still dominated by fossil energy,and non-fossil energy is also growing steadily.The CO₂generated by fossil energy has caused a series of energy and environmental problems.At the same time,the difficulty of storing excess electric energy has also become an urgent problem to be solved.Electrocatalytic carbon dioxide reduction reaction（CO₂RR）can convert CO₂ into value-added fuels and chemicals.The products can also be used as energy carrier molecules to store electrical energy.The artificial closure of the carbon cycle can not only alleviate the"greenhouse effect",but also contribute to the achievement of the"two-carbon"goal.The study of copper-based catalysts for the production of multi-carbon products(C₂₊)from CO₂RR is a topic with great research potential and challenges.Copper is one of the few metal that can efficiently electroreduce CO₂ to multi-carbon olefins or alcohols.However,its reduction products are extremely complex and the side reaction of hydrogen evolution is serious.Therefore,the C₂₊Faradaic efficiency and the activity is low and the stability of catalysts is poor.Finding and studying the real catalytic active sites and generation mechanism of C₂₊is particularly important for this research direction,which is also the key to controlling its selectivity.To improve the selectivity of C₂₊,the chemical behavior of CO^（9）needs to be regulated so that it develops in the direction of^（9）C₂.The nanostructure,electronic structure and chemical environmental of Cu are closely related to the adsorption activation and transformation activation energy of key intermediates.The research in this paper is as follows:（1）Pre-catalysts of copper catalysts were synthesized by precipitation method.First,the copper produced by electrochemical reconfiguration of different precursors during the synthesis process was studied for CO₂RR.Cu O-derived copper（OD-Cu）achieved high C₂₊selectivity（78%）and partial current density(663 m A cm^-2)because of its large specific surface area and complex grain boundaries network of（111）/（100）.The synergistic effect of crystal facets on C₂₊selectivity was investigated by adjusting the facets ratio of Cu（111）to Cu（100）.The facet effect of O-D Cu crystal promote the selectivity of C₂₊owing to the high coverage with different configurations,subsequent hydrogenation and C-C coupling reaction process of^（9）CO.（2）A gold-copper composite material was prepared by thermal reduction and high-temperature hydrogen reduction strategy.The Au particles with a size of about 10nm were supported on the copper carrier.Au provides Cu with a surface^（9）CO-rich chemical environment,which improves the efficiency of Cu for C-C coupling.Compared with pure copper material,the Au/Cu-H300 composite exhibited better CO₂RR performance and significantly improved the Faradaic efficiency of n-propanol（n-Pr OH）.Au and Cu synergistically promote the produce of^（9）C₂and coupling of^（9）C₂and^（9）C₁.By adjusting the loading of Au,it is found that the Faradaic efficiency of n-Pr OH can reach 14%,which is more than 4 times that of pure copper.The tandem catalyst designed in this chapter provides an idea for preparing copper-based catalysts with high C3 product selectivity.更多还原