Hsu Jason, Houache Mohamed S E, Abu-Lebdeh Yaser, Patton Witt Reagan, Guzman Marcelo I, Al-Abadleh Hind A
Department of Chemistry and Biochemistry, Wilfrid Laurier University, Waterloo, Ontario, Canada K1A 0R6.
National Research Council of Canada, Energy, Mining and Environment Ottawa, Ontario, Canada K1A 0R6.
Langmuir. 2024 Jan 30;40(4):2377-2384. doi: 10.1021/acs.langmuir.3c03660. Epub 2024 Jan 17.
Formate (HCOO) is the most dominant intermediate identified during carbon dioxide electrochemical reduction (COER). While previous studies showed that copper (Cu)-based materials that include Cu(0), CuO, and CuO are ideal catalysts for COER, challenges to scalability stem from low selectivity and undesirable products in the -1.0-1.0 V range. There are few studies on the binding mechanism of intermediates and products for these systems as well as on changes to surface sites upon applying potential. Here, we use an in situ approach to study the redox surface chemistry of formate on Cu thin films deposited on Si wafers using a VeeMAX III spectroelectrochemical (SEC) cell compatible with attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). Spectra for surface species were collected in real time as a function of applied potential during cyclic voltammetry (CV) experiments. Results showed the reproducibility of CV curves on freshly prepared Cu/Si wafers with relatively high signal-to-noise ATR-FTIR absorbance features of surface species during these electrochemical experiments. The oxidation reaction of HCOO to bicarbonate (HCO) was observed using ATR-FTIR at a voltage of 0.27 V. Samples were then subjected to reduction in the CV, and the aqueous phase products below the detection limit of the SEC-ATR-FTIR were identified using ion chromatography (IC). We report the formation of glycolate (HCO) and glyoxylate (HCO) with trace amounts of oxalate (CO), indicating that C-C coupling reactions proceed in these systems. Changes to the oxidation state of surface Cu were measured using X-ray photoelectron spectroscopy, which showed a reduction in Cu(0) and an increase in Cu(OH), indicating surface oxidation.
甲酸盐（HCOO）是在二氧化碳电化学还原（COER）过程中鉴定出的最主要中间体。虽然先前的研究表明，包括Cu(0)、CuO和CuO的铜（Cu）基材料是COER的理想催化剂，但规模化面临的挑战源于在-1.0至1.0 V范围内选择性低和产生不需要的产物。关于这些体系中中间体和产物的结合机制以及施加电位时表面位点的变化，研究较少。在这里，我们采用原位方法，使用与衰减全反射傅里叶变换红外光谱（ATR-FTIR）兼容的VeeMAX III光谱电化学（SEC）池，研究沉积在硅片上的Cu薄膜上甲酸盐的氧化还原表面化学。在循环伏安法（CV）实验中，作为施加电位的函数实时收集表面物种的光谱。结果表明，在这些电化学实验中，新鲜制备的Cu/Si晶片上CV曲线具有可重复性，表面物种具有相对较高的信噪比ATR-FTIR吸收特征。在0.27 V的电压下，使用ATR-FTIR观察到HCOO氧化为碳酸氢盐（HCO）的反应。然后在CV中对样品进行还原，并使用离子色谱（IC）鉴定低于SEC-ATR-FTIR检测限的水相产物。我们报告了乙醇酸盐（HCO）和乙醛酸盐（HCO）的形成以及痕量草酸盐（CO）的形成，表明这些体系中发生了C-C偶联反应。使用X射线光电子能谱测量表面Cu的氧化态变化，结果表明Cu(0)减少，Cu(OH)增加，表明表面发生了氧化。
