Ou Lihui, Zhao Kexin
Hunan Province Cooperative Innovation Center for the Construction & Development of Dongting Lake Ecologic Economic Zone, College of Chemistry and Materials Engineering, Hunan University of Arts and Science, Changde 415000, China.
ACS Omega. 2019 Oct 11;4(17):17269-17278. doi: 10.1021/acsomega.9b01917. eCollection 2019 Oct 22.
Potential-dependent CO electroreduction pathways on Cu(111) are systematically studied with the aim of applying an improved electrode/aqueous interface model in this paper. The results indicate that our present defined CHO and CHOH pathways may be able to parallelly take place at low overpotentials. Notably, the applied potentials will not alter the optimal CO reduction mechanisms. However, the presence of high overpotentials makes CO electroreduction more favorable, thus explaining why high overpotentials at experiments are required during CO electroreduction on Cu. Based on the potential-dependent energetics, the results suggest that COOH and CHO intermediates may be unstable at low overpotentials, in which COOH can easily change back to CO and CHO can easily change back to CO, thus preventing CO electroreduction. However, the high overpotentials will facilitate the formation and further electroreduction of CO and CHO. Thus, we can speculate that CO formation and then further electroreduction into CHO are the possible potential-limiting steps during CO electroreduction, which are regarded as the origin of experimentally observed high overpotentials. The present comprehensive understanding on CO electroreduction pathways can provide theoretical guidelines for efficiently designing Cu-based alloy electrocatalysts operated under the conditions of low overpotentials.
本文旨在应用改进的电极/水界面模型，系统地研究了Cu(111)上电位依赖的CO电还原途径。结果表明，我们目前定义的CHO和CHOH途径可能在低过电位下平行发生。值得注意的是，施加的电位不会改变最佳的CO还原机制。然而，高过电位的存在使CO电还原更有利，从而解释了为什么在Cu上进行CO电还原实验时需要高过电位。基于电位依赖的能量学，结果表明COOH和CHO中间体在低过电位下可能不稳定，其中COOH容易变回CO，CHO容易变回CO，从而阻止了CO电还原。然而，高过电位将促进CO和CHO的形成及进一步电还原。因此，我们可以推测，CO的形成然后进一步电还原为CHO是CO电还原过程中可能的电位限制步骤，这被认为是实验观察到的高过电位的起源。目前对CO电还原途径的全面理解可为在低过电位条件下高效设计Cu基合金电催化剂提供理论指导。
