Baumgartner Lorenz M, Koopman Christel I, Forner-Cuenca Antoni, Vermaas David A
Department of Chemical Engineering, Delft University of Technology, Van der Maasweg 9, 2629 HZDelft, Netherlands.
Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, Het Kranenveld 14, 5612 AZEindhoven, Netherlands.
ACS Appl Energy Mater. 2022 Dec 26;5(12):15125-15135. doi: 10.1021/acsaem.2c02783. Epub 2022 Dec 8.
Electrochemical CO reduction has the potential to use excess renewable electricity to produce hydrocarbon chemicals and fuels. Gas diffusion electrodes (GDEs) allow overcoming the limitations of CO mass transfer but are sensitive to flooding from (hydrostatic) pressure differences, which inhibits upscaling. We investigate the effect of the flooding behavior on the CO reduction performance. Our study includes six commercial gas diffusion layer materials with different microstructures (carbon cloth and carbon paper) and thicknesses coated with a Ag catalyst and exposed to differential pressures corresponding to different flow regimes (gas breakthrough, flow-by, and liquid breakthrough). We show that physical electrowetting further limits the flow-by regime at commercially relevant current densities (≥200 mA cm), which reduces the Faradaic efficiency for CO (FE) for most carbon papers. However, the carbon cloth GDE maintains its high CO reduction performance despite being flooded with the electrolyte due to its bimodal pore structure. Exposed to pressure differences equivalent to 100 cm height, the carbon cloth is able to sustain an average FE of 69% at 200 mA cm even when the liquid continuously breaks through. CO electrolyzers with carbon cloth GDEs are therefore promising for scale-up because they enable high CO reduction efficiency while tolerating a broad range of flow regimes.
电化学CO还原有潜力利用多余的可再生电力来生产碳氢化合物化学品和燃料。气体扩散电极（GDEs）能够克服CO传质的限制，但对（静水）压差引起的水淹敏感，这阻碍了其放大应用。我们研究了水淹行为对CO还原性能的影响。我们的研究包括六种具有不同微观结构（碳布和碳纸）和厚度的商业气体扩散层材料，这些材料涂覆有Ag催化剂，并暴露于对应不同流动状态（气体突破、旁流和液体突破）的压差下。我们表明，在商业相关电流密度（≥200 mA cm）下，物理电润湿进一步限制了旁流状态，这降低了大多数碳纸的CO法拉第效率（FE）。然而，碳布GDE尽管因电解液水淹，但其双峰孔隙结构使其仍能保持较高的CO还原性能。即使液体持续突破，在相当于100 cm高度的压差下，碳布在200 mA cm时仍能维持平均69%的FE。因此，具有碳布GDE的CO电解槽有望扩大规模，因为它们能够实现高CO还原效率，同时能耐受广泛的流动状态。
