State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemical Engineering, Nanjing Tech University, Nanjing, 211816, China.
Department of Physics and Astronomy, National Graphene Institute, University of Manchester, Manchester, M13 9PL, UK.
Proc Natl Acad Sci U S A. 2022 Jul 19;119(29):e2118166119. doi: 10.1073/pnas.2118166119. Epub 2022 Jul 14.
Electrochemical reduction of CO to value-added chemicals and fuels is a promising strategy to sustain pressing renewable energy demands and to address climate change issues. Direct observation of reaction intermediates during the CO reduction reaction will contribute to mechanistic understandings and thus promote the design of catalysts with the desired activity, selectivity, and stability. Herein, we combined in situ electrochemical shell-isolated nanoparticle-enhanced Raman spectroscopy and ab initio molecular dynamics calculations to investigate the CORR process on Cu single-crystal surfaces in various electrolytes. Competing redox pathways and coexistent intermediates of CO adsorption (*CO and *CO), dimerization (protonated dimer *HOCCOH and its dehydrated *CCO), oxidation (*CO and *CO), and hydrogenation (*CHO), as well as Cu-O/Cu-OH species at Cu-electrolyte interfaces, were simultaneously identified using in situ spectroscopy and further confirmed with isotope-labeling experiments. With AIMD simulations, we report accurate vibrational frequency assignments of these intermediates based on the calculated vibrational density of states and reveal the corresponding species in the electrochemical CO redox landscape on Cu surfaces. Our findings provide direct insights into key intermediates during the CORR and offer a full-spectroscopic tool (40-4,000 cm) for future mechanistic studies.
电化学还原 CO 为高附加值化学品和燃料是一种很有前途的策略，可以满足紧迫的可再生能源需求并解决气候变化问题。在 CO 还原反应过程中直接观察反应中间体有助于深入了解反应机理，从而促进具有所需活性、选择性和稳定性的催化剂的设计。在此，我们结合了原位电化学壳层隔离纳米粒子增强拉曼光谱和从头算分子动力学计算，研究了在不同电解液中 Cu 单晶表面上的 CORR 过程。利用原位光谱和同位素标记实验进一步证实，我们同时鉴定了 CO 吸附（CO 和 CO）、二聚（质子化二聚体HOCCOH 和其脱水CCO）、氧化（*CO 和 *CO）和加氢（*CHO）的竞争氧化还原途径和共存中间体，以及 Cu-电解质界面上的 Cu-O/Cu-OH 物种。通过 AIMD 模拟，我们根据计算得到的振动态密度对这些中间体的准确振动频率进行了分配，并揭示了 Cu 表面上电化学 CO 氧化还原景观中的相应物种。我们的研究结果为 CORR 过程中的关键中间体提供了直接的认识，并为未来的机理研究提供了一种全光谱工具（40-4,000 cm）。
