Subramanian Siddhartha, Middelkoop Joost, Burdyny Thomas
Materials for Energy Conversion and Storage (MECS), Department of Chemical Engineering, Faculty of Applied Sciences, Delft University of Technology van der Maasweg 9 2629 HZ Delft The Netherlands
Sustain Energy Fuels. 2021 Oct 27;5(23):6040-6048. doi: 10.1039/d1se01534f. eCollection 2021 Nov 23.
The production of value added C1 and C2 compounds within CO electrolyzers has reached sufficient catalytic performance that system and process performance - such as CO utilization - have come more into consideration. Efforts to assess the limitations of CO conversion and crossover within electrochemical systems have been performed, providing valuable information to position CO electrolyzers within a larger process. Currently missing, however, is a clear elucidation of the inevitable trade-offs that exist between CO utilization and electrolyzer performance, specifically how the faradaic efficiency of a system varies with CO availability. Such information is needed to properly assess the viability of the technology. In this work, we provide a combined experimental and 3D modelling assessment of the trade-offs between CO utilization and selectivity at 200 mA cm within a membrane-electrode assembly CO electrolyzer. Using varying inlet flow rates we demonstrate that the variation in spatial concentration of CO leads to spatial variations in faradaic efficiency that cannot be captured using common 'black box' measurement procedures. Specifically, losses of faradaic efficiency are observed to occur even at incomplete CO consumption (80%). Modelling of the gas channel and diffusion layers indicated that at least a portion of the H generated is considered as avoidable by proper flow field design and modification. The combined work allows for a spatially resolved interpretation of product selectivity occurring inside the reactor, providing the foundation for design rules in balancing CO utilization and device performance in both lab and scaled applications.
在一氧化碳电解槽中生产增值的C1和C2化合物已达到足够的催化性能，以至于系统和工艺性能（如一氧化碳利用率）已得到更多考虑。人们已努力评估电化学系统中一氧化碳转化和交叉的局限性，为将一氧化碳电解槽置于更大的工艺中提供了有价值的信息。然而，目前缺少的是对一氧化碳利用率和电解槽性能之间不可避免的权衡的清晰阐释，特别是系统的法拉第效率如何随一氧化碳可用性而变化。此类信息对于正确评估该技术的可行性是必要的。在这项工作中，我们对膜电极组件一氧化碳电解槽中200 mA/cm²下一氧化碳利用率和选择性之间的权衡进行了实验和三维建模相结合的评估。通过改变入口流速，我们证明一氧化碳空间浓度的变化会导致法拉第效率的空间变化，而这是使用常见的“黑箱”测量程序无法捕捉到的。具体而言，即使在一氧化碳消耗不完全（80%）的情况下，也观察到法拉第效率的损失。对气体通道和扩散层的建模表明，通过适当的流场设计和改进，至少一部分产生的氢气可被视为可避免的。这项综合工作使得能够对反应器内部发生的产物选择性进行空间分辨解释，为在实验室和规模化应用中平衡一氧化碳利用率和装置性能的设计规则奠定了基础。
