Electrocatalytic reduction of CO2 to ethylene and ethanol through hydrogen-assisted C-C coupling over fluorine-modified copper

精准控制C1分子C-C偶联合成特定C2+化合物是C1化学中极具挑战性的难题。由于C2+化合物(如乙烯和乙醇)在化工和能源领域具有重要用途，将CO2直接转化为C2+产物极具吸引力。发展高效催化剂，实现高电流密度、高C2+选择性、高稳定性的“三高”性能，是推进电催化还原CO2走向实际应用的关键。研究团队针对电催化还原CO2中高CO2还原法拉第效率的催化剂常常活性低的问题，提出了适当提高催化剂活化水的能力对增加CO2还原活性的重要性，发展出氢助碳碳偶联(hydrogen-assisted C-C coupling)的新策略，在氟修饰的铜(F-Cu)催化剂上实现了CO2电催化还原制乙烯和乙醇的新突破。该研究工作实验部分主要由王野、张庆红教授指导，能源材料协同创新中心iChEM2016级博士生马文超、固体表面物理化学国家重点实验室高级工程师谢顺吉(共同第一作者)完成；理论计算部分由程俊教授指导，2017级硕士生刘彤彤(共同第一作者)、2016级博士生樊祺源完成。叶进裕博士为原位红外测试提供了支持。上海光源姜政研究员、孙凡飞博士、杨若欧为同步辐射表征提供了支持。 这是投稿的最终版本，正式出版的论文版本请访问官方链接（https://doi.org/10.1038/s41929-020-0450-0）。Electrocatalytic reduction of CO2 into multi-carbon (C2+) products is a highly attractive route for CO2 utilization. However, the yield of C2+ products remains low because of the limited C2+ selectivity at high CO2 conversion rate. Here, we report a fluorine-modified copper catalyst that exhibits an ultrahigh current density of 1.6 A cm−2 at C2+ (mainly ethylene and ethanol) Faradaic efficiency of 80% for electrocatalytic CO2 reduction in a flow cell. The C2-4 selectivity reaches 85.8% at a single-pass yield of 16.5%. We show a hydrogen-assisted C−C coupling mechanism between adsorbed formyl (CHO) intermediates for C2+ formation. Fluorine enhances water activation, CO adsorption and hydrogenation of adsorbed CO to CHO intermediate that can readily undergo coupling. Our findings offer an opportunity to design highly active and selective CO2 electroreduction catalysts with potential for practical applicationThis work was supported by the National Key Research and Development Program of the Ministry of Science and Technology of China (No. 2017YFB0602201), the National Natural Science Foundation of China (Nos. 21690082, 91545203, 21503176 and 21802110), We thank staffs at the BL14W1 beamline of the Shanghai Synchrotron Radiation Facilities (SSRF) for assistance with the EXAFS measurements.研究工作得到科技部重点研发计划（批准号：2017YFB0602201）和国家自然科学基金（批准号：21690082、91545203、21503176、21802110）项目的资助

Identifying the Conformational Isomers of Single-Molecule Cyclohexane at Room Temperature

构象异构是化学中的基本问题。然而对于环己烷等柔性分子，由于其在室温下极快的互变异构过程，基于系综的表征方法（如核磁等）只能得到所有构象平均贡献的结果。为了应对这一挑战，化学化工学院洪文晶教授与夏海平教授课题组为在室温条件下对柔性分子构象的定量分析与表征这一挑战，课题组成功实现了在室温条件下对环己烷两种椅式构象的电学表征与比例识别。同时，通过纳米电极间隙对分子的限域作用，发现在宏观尺度下极不稳定的扭船式中间体得以在单分子尺度稳定存在，这为不稳定中间体的研究提供了重要表征方法。 这一研究工作是在化学化工学院洪文晶教授、夏海平教授共同指导下完成的，iChEM直博生唐淳与化工系研究生唐永翔为论文共同第一作者。师佳副教授与刘俊扬副研究员为该工作提供了指导，博士后陈志昕、博士研究生陈李珏以及研究生叶艺玲、严哲玮、张珑漪共同参与了该工作。【Abstract】Isomerism reflects the ubiquitous nature that molecules with the same molecular formula show different structures. The interconversion between conformational isomers of flexible molecules is quite fast owing to the low barriers of around 10 kcal mol−1, leading to average signal contributed by all the possible isomers characterized by ensemble methods. On this account, identifying the conformational isomers of flexible molecules at room temperature has a substantial challenge. Here, we develop a single-molecule approach to identify the conformational isomers of cyclohexane at room temperature through the single-molecule electrical characterization. By noise analysis and feature extraction of the conductance of single-molecule junctions, we quantificationally identified two chair isomers of cyclohexane at room temperature, while such identification is only feasible at low temperatures by ensemble characterization. The strategy to apply the single-molecule approach to identify conformational isomers paves the avenue to investigate the isomerization of flexible molecules beyond the ensemble methods.This work was supported by the National Natural Science Foundation of China (nos, 21722305, 21673195, 21703188, and U1705254), the National Key R&D Program of China (2017YFA0204902), China Postdoctoral Science Foundation (no. 2017M622060), and the Fundamental Research Funds for Xiamen University (20720190002).该工作获得了科技部国家重点研发计划、国家自然科学基金等项目的资助，也得到了固体表面物理化学国家重点实验室、能源材料化学协同创新中心的支持