Bondue Christoph J, Graf Matthias, Goyal Akansha, Koper Marc T M
Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands.
Institute for Materials Research, Helmholtz Center Geesthacht, Max-Planck-Straße 1, Geesthacht 21502, Germany.
J Am Chem Soc. 2021 Jan 13;143(1):279-285. doi: 10.1021/jacs.0c10397. Epub 2020 Dec 24.
In this article we investigate the electrochemical reduction of CO at gold electrodes under mildly acidic conditions. Differential electrochemical mass spectroscopy (DEMS) is used to quantify the amounts of formed hydrogen and carbon monoxide as well as the consumed amount of CO. We investigate how the Faradaic efficiency of CO formation is affected by the CO partial pressure (0.1-0.5 bar) and the proton concentration (1-0.25 mM). Increasing the former enhances the rate of CO reduction and suppresses hydrogen evolution from proton reduction, leading to Faradaic efficiencies close to 100%. Hydrogen evolution is suppressed by CO reduction as all protons at the electrode surfaces are used to support the formation of water (CO + 2H + 2e → CO + HO). Under conditions of slow mass transport, this leaves no protons to support hydrogen evolution. On the basis of our results, we derive a general design principle for acid CO electrolyzers to suppress hydrogen evolution from proton reduction: the rate of CO/OH formation must be high enough to match/compensate the mass transfer of protons to the electrode surface.
在本文中，我们研究了在弱酸性条件下金电极上一氧化碳的电化学还原。采用差分电化学质谱（DEMS）对生成的氢气和一氧化碳的量以及消耗的一氧化碳量进行定量分析。我们研究了一氧化碳形成的法拉第效率如何受到一氧化碳分压（0.1 - 0.5巴）和质子浓度（1 - 0.25毫摩尔）的影响。增加前者会提高一氧化碳还原的速率，并抑制质子还原产生氢气，从而使法拉第效率接近100%。由于电极表面的所有质子都用于支持水的形成（CO + 2H⁺ + 2e⁻ → CO + H₂O），一氧化碳还原抑制了氢气的析出。在传质缓慢的条件下，这使得没有质子来支持氢气的析出。基于我们的研究结果，我们推导出了一种用于酸性一氧化碳电解槽抑制质子还原产生氢气的通用设计原则：一氧化碳/羟基的形成速率必须足够高，以匹配/补偿质子向电极表面的传质。
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