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在电化学CO2还原反应中, 合理调节关键中间体*CO的吸附构型可以促进碳-碳（C-C）偶联生成多碳产物。
近日，天津大学张志成教授和中国科学院深圳先进技术研究院孙源淼研究员等人在Science China Materials发表研究论文，分别从理论和实验的角度证实了顶式吸附的*CHO和三重位吸附的*CO有利于在Cu位点上进行C-C耦合，实现高选择性的电化学CO2还原为乙醇。
本文要点
1) 理论计算表明，通过顶式吸附的*CHO和三重位吸附的*CO在Cu位点上进行C-C耦合是一种能量有利的途径。2) 作为概念验证，制备了串联三金属AuAgCu异质结（Au@Ag/Cu），其中Au@Ag位点上顶式吸附的*CO溢流到Cu位点后转变为三重位吸附，然后该三重位吸附的*CO和Cu位点上顶式吸附的*CHO进行不对称C-C偶联，促进了乙醇产物的形成。在−0.3 V vs. RHE的低电位下，乙醇法拉第效率最高为65.9%。这项工作通过调节中间产物的吸附构型，为串联催化的内在机制提供了新的见解。
Figure 1. Theoretical calculations of the adsorption behaviors of key CO2RR intermediates and the subsequent C–C coupling process. (a) The calculated adsorption energy of *CO on Ag surface, Ag/Cu interface and Cu surface. (b) The calculated adsorption energy of *CO with different adsorption configuration on Cu surface sites. (c) The free energy of C–C coupling between *CHO and *CO on different Cu surface sites. Schematic illustration of the overall mechanism of C–C formation on (d) Au@Ag@Cu core-shell structure and (e) tandem Au/Ag/Cu catalyst.![]()
Figure 2. Morphology and structural characterization of Au@Ag/Cu heterojunction (b–e) and Au@Ag@Cu core-shell structure (f–i). (a) Synthesis scheme of Au@Ag/Cu heterojunction and Au@Ag@Cu core-shell structure. (b, c) Spherical aberration-corrected high-resolution HAADF-STEM images. (d, e) HAADF-STEM image and corresponding EDS elemental mapping. (f, g) Spherical aberration-corrected high-resolution HAADF-STEM images. (h, i) HAADF-STEM image and corresponding EDS elemental mapping.![]()
Figure 3. Comparison of the electrochemical CO2RR performances in flow cell. (a) Schematic illustration of the flow cell. (b) LSV curves performed in Ar and CO2 atmosphere in 1 M KOH solution. FE and the product distribution at different potentials of (c) Au@Ag/Cu heterojunction, (d) Au@Ag@Cu core-shell structure, and (e) Au@Ag NRs. Comparison of (f) FE and (g) partial current density of C2H5OH with different catalysts. (h) Overall performance comparison between Au@Ag NRs, Au@Ag/Cu heterojunction, and Au@Ag@Cu core-shell structure for CO2-to-C2H5OH conversion. (i) Comparison of applied potential and FEC2H5OH for Au@Ag/Cu heterojunction and other previously reported Cu-based catalysts. ![]()
Figure 4. In situ ATR-FTIR. Potential-dependent in situ ATR-FTIR spectra of (a) Au@Ag/Cu heterojunction, (b) Au@Ag@Cu core-shell structure, and (c) Au@Ag NRs in CO2-saturated 0.1 M KHCO3 electrolyte. The adsorption configurations of *CO or *CHO on (d) Au@Ag/Cu heterojunction, (e) Au@Ag@Cu core-shell structure, and (f) Au@Ag NRs.Yongxia Shi, Junjun Li, Zhiwen Min, Xinyi Wang, Man Hou, Hao Ma, Zechao Zhuang, Yuchen Qin, Yuanmiao Sun, Dingsheng Wang, Zhicheng Zhang. Adjusting *CO adsorption configuration over tandem trimetallic AuAgCu heterojunction boosts CO2 electroreduction to ethanol via asymmetric C–C coupling. Sci. China Mater. (2024).https://doi.org/10.1007/s40843-024-3162-2
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