Deacon-Price Connor, da Silva Alisson H M, Santana Cássia S, Koper Marc T M, Garcia Amanda C
Van't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands.
Leiden Institute of Chemistry, Leiden University, Gorlaeus Laboratories, P.O. Box 9502, 2300 RA, Leiden, The Netherlands.
J Phys Chem C Nanomater Interfaces. 2023 Jul 12;127(29):14518-14527. doi: 10.1021/acs.jpcc.3c03257. eCollection 2023 Jul 27.
The electrochemical reduction of CO (CORR) is a sustainable alternative for producing fuels and chemicals, although the production of highly desired hydrocarbons is still a challenge due to the higher overpotential requirement in combination with the competitive hydrogen evolution reaction (HER). Tailoring the electrolyte composition is a possible strategy to favor the CORR over the HER. In this work we studied the solvent effect on the CORR on a nanostructured Cu electrode in acetonitrile solvent with different amounts of water. Similar to what has been observed for aqueous media, our online gas chromatography results showed that CORR in acetonitrile solvent is also structure-dependent, since nanocube-covered copper (CuNC) was the only surface (in comparison to polycrystalline Cu) capable of producing a detectable amount of ethylene (10% FE), provided there is enough water present in the electrolyte (>500 mM). In situ Fourier Transform Infrared (FTIR) spectroscopy showed that in acetonitrile solvent the presence of CO strongly inhibits HER by driving away water from the interface. CO is by far the main product of CORR in acetonitrile (>85% Faradaic efficiency), but adsorbed CO is not detected. This suggests that in acetonitrile media CO adsorption is inhibited compared to aqueous media. Remarkably, the addition of water to acetonitrile has little quantitative and almost no qualitative effect on the activity and selectivity of the CORR. This indicates that water is not strongly involved in the rate-determining step of the CORR in acetonitrile. Only at the highest water concentrations and at the CuNC surface, the CO coverage becomes high enough that a small amount of C product is formed.
CO的电化学还原（CORR）是生产燃料和化学品的一种可持续替代方法，尽管由于与竞争性析氢反应（HER）结合需要更高的过电位，生产高附加值的碳氢化合物仍然是一项挑战。调整电解质组成是一种使CORR优于HER的可能策略。在这项工作中，我们研究了在含有不同水量的乙腈溶剂中，溶剂对纳米结构铜电极上CORR的影响。与在水性介质中观察到的情况类似，我们的在线气相色谱结果表明，乙腈溶剂中的CORR也是结构依赖性的，因为与多晶铜相比，纳米立方体覆盖的铜（CuNC）是唯一能够产生可检测量乙烯（10%法拉第效率）的表面，前提是电解质中存在足够的水（>500 mM）。原位傅里叶变换红外（FTIR）光谱表明，在乙腈溶剂中，CO的存在通过将水从界面驱离而强烈抑制HER。到目前为止，CO是乙腈中CORR的主要产物（>85%法拉第效率），但未检测到吸附的CO。这表明与水性介质相比，在乙腈介质中CO吸附受到抑制。值得注意的是，向乙腈中添加水对CORR的活性和选择性几乎没有定量和定性影响。这表明水在乙腈中CORR的速率决定步骤中没有强烈参与。只有在最高水浓度和CuNC表面，CO覆盖率才会变得足够高，从而形成少量的C产物。
