物理化学学报

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富氧空位的非晶氧化铜高选择性电催化还原CO2制乙烯

韦天然1, 张书胜2, 刘倩3, 邱园4, 罗俊4,5, 刘熙俊1   

  1. 1. 广西大学有色金属及材料加工新技术教育部重点实验室, 广西有色金属及特色材料加工重点实验室, 资源环境与材料学院, 南宁 53004;
    2. 郑州大学化学学院, 郑州 450000;
    3. 成都大学高等研究院, 成都 610106;
    4. 电子科技大学深圳高等研究院, 广东 深圳 518110;
    5. 天津理工大学新能源材料与低碳技术研究院, 材料科学与工程学院, 天津 300384
  • 收稿日期:2022-07-12 修回日期:2022-08-29 录用日期:2022-09-08 发布日期:2022-09-15
  • 通讯作者: 刘熙俊 E-mail:xjliu@tjut.edu.cn
  • 基金资助:
    国家自然科学基金(22075211,21601136,51971157,51621003),天津市杰出青年科学基金(19JCJQJC61800)资助项目

Oxygen Vacancy-Rich Amorphous Copper Oxide Enables Highly Selective Electroreduction of Carbon Dioxide to Ethylene

Tianran Wei1, Shusheng Zhang2, Qian Liu3, Yuan Qiu4, Jun Luo4,5, Xijun Liu1   

  1. 1. MOE Key Laboratory of New Processing Technology for Non-Ferrous Metals and Materials, and Guangxi Key Laboratory of Processing for Non-Ferrous Metals and Featured Materials, School of Resource, Environments and Materials, Guangxi University, Nanning 530004, China;
    2. College of Chemistry, Zhengzhou University, Zhengzhou 450000, China;
    3. Institute for Advanced Study, Chengdu University, Chengdu 610106, China;
    4. Shenzhen Institute for Advanced Study, University of Electronic Science and Technology of China, Shenzhen 518110, Guangdong Province, China;
    5. Institute for New Energy Materials and Low-Carbon Technologies, School of Materials Science and Engineering, Tianjin University of Technology, Tianjin 300384, China
  • Received:2022-07-12 Revised:2022-08-29 Accepted:2022-09-08 Published:2022-09-15
  • Contact: Xijun Liu E-mail:xjliu@tjut.edu.cn
  • Supported by:
    The project was supported by the National Natural Science Foundation of China (22075211,21601136,51971157,51621003),and Tianjin Science Fund for Distinguished Young Scholars (19JCJQJC61800).

摘要: 过量化石能源的消耗导致大气中的二氧化碳含量不断上升,由此引发包括温室效应在内的环境问题。对此,常温常压下的电催化二氧化碳还原手段为制备高附加值的化工原料和实现碳循环提供了一种很有前景的技术储备。在众多的二氧化碳还原产物中,碳氢化合物尤其是乙烯,它作为塑料和其他化工产品的重要原料受到广泛的关注。电催化二氧化碳还原制乙烯工艺不仅可适配于现有的生产设备也可作为取代目前工业化的裂解方法。近年来,研究者们为了开发高效的电催化二氧化碳还原制乙烯催化剂开展了大量的研究。不过值得注意的是,大部分研究集中于铜基材料。尽管目前研究者取得了很多成果,但仍缺少可高选择性产乙烯的二氧化碳还原催化剂。如何设计出可活化二氧化碳分子,同时对*CO和*COH中间物有强吸附能力的催化剂是研究难点。针对此问题,本文中通过真空蒸镀的方法制备出一种富氧空位的非晶氧化铜纳米薄膜催化剂。受益于纳米薄膜的构建和氧空位的引入,该催化剂可快速进行电荷和物质的交换,并利于二氧化碳分子的吸附及优化还原中间产物的亲和力,进而表现出优异的电催化二氧化碳制乙烯的性能。结果表明,在加有0.1 mol∙L−1碳酸氢钾溶液的H型电解池中测试中,该催化剂在相对于可逆氢电极电势为−1.3 V的产乙烯法拉第效率可达85% ±3%。此外,该催化剂在长达48 h的电催化还原过程中仍可保持高的乙烯选择性。这些指标与已报道的最好的铜基催化剂的性能相当。另外,结构和化学手段表明该催化剂在电解反应中可保持良好的稳定性。进一步,我们测试了该催化剂在膜电极体系的性能,结果表明该催化剂的最大乙烯局部电流密度可达115.4 mA∙cm−2 (操作电压为−1.95 V),最高法拉第效率可达78% ±2% (操作电压为−1.75 V)。理论和实验结果证明该催化剂的高乙烯选择性源于引入的氧空位不仅有利于二氧化碳分子的吸附,而且可增强对*CO和*COH的亲和力。本论文的研究不仅可激发学术界对高乙烯选择性的非晶铜基材料开发,同时在一定程度上提供有关电催化二氧化碳制乙烯的反应机制认识。

关键词: 二氧化碳固定, 二碳产物, 电催化, 非晶催化剂, 铜氧化物

Abstract: The ever-increasing carbon dioxide (CO2) emissions caused by excessive fossil fuel consumption induce environmental issues such as global warming. To overcome this, the electrocatalytic CO2 reduction (ECR) under ambient conditions offers an appealing approach for converting CO2 to value-added chemicals and realizing a closed carbon loop. Among the ECR products, ethylene (C2H4), an important building block for plastics and other chemicals, has attracted considerable attention owing to its compatibility with existing infrastructure and the promising substitution of industrial steam cracking. In recent years, numerous efforts have been devoted to developing highly active and selective catalysts for converting CO2 to C2H4, with most studies having focused on Cu-based materials. Despite the significant advancements made to date, the development of the ECR-to-C2H4 process is still hindered by the lack of suitable catalysts that can effectively activate CO2 and strengthen the surface binding of *CO and *COH species. In this study, an amorphous copper oxide (CuOx) nanofilm that is rich in oxygen vacancies was prepared via a facile vacuum evaporation method for the efficient electrocatalytic conversion of CO2 to C2H4. It was expected that the nano-scale electrode thickness would greatly accelerate charge- and mass-transfer during CO2 electrolysis. Moreover, the introduction of oxygen vacancies favored the adsorption of CO2 and intermediates. As a result, in a typical H-cell, the synthesized defective catalyst delivered a maximum Faradaic efficiency of 85 ±3% at −1.3 V versus the reversible hydrogen electrode and maintained a stable C2H4 selectivity over 48 h in a 0.1 M potassium bicarbonate solution. Interestingly, the performance observed with the synthesized electrocatalyst in this study is comparable with that of state-of-the-art Cu-based ECR catalysts. Additional structural and chemical characterizations confirmed the robust nature of the as-prepared catalyst. Moreover, when the catalyst was utilized in a membrane electrode assembly cell, it achieved a maximum C2H4 partial current density of approximately 115.4 mA∙cm-2 at a cell voltage of −1.95 V and Faradaic efficiency of 78 ±2% at a cell voltage of −1.75 V. Furthermore, theoretical and experimental analyses revealed that oxygen defects not only favored CO2 adsorption but also enabled strong affinities for *CO and *COH intermediates, which synergistically contributed to a high selectivity for C2H4 formation. We believe that our present work will motivate the exploration of amorphous Cu-based materials for achieving efficient CO2-to-C2H4 electrolysis and be a guide towards fundamentally understanding the mechanism of catalytic CO2 reduction.

Key words: CO2 fixation, C2 product, Electrocatalysis, Amorphous catalyst, Cu oxide

MSC2000: 

  • O646