Carbon dioxide capture underpins an important range of technologies that can help to mitigate climate change. Improved carbon capture technologies that are driven by electrochemistry are under active development and it was recently found that supercapacitor energy storage devices can reversibly capture and release carbon dioxide. So-called supercapacitive swing adsorption (SSA) has several advantages over traditional carbon dioxide capture technologies such as lower energy consumption and the use of non-toxic materials. However, the mechanism for the capture of CO2 in these devices is poorly understood, making it challenging to design improved systems¬. Here the mechanism of SSA is investigated via finite-element modelling with COMSOL of aqueous continuum transport equations, coupled to the CO2 to bicarbonate reaction. This simple computational model reproduces the key experimental observations and shows that charging leads to bicarbonate depletion (or accumulation) in the electrodes, driving CO2 capture (or release) at the gas-exposed electrode. This suggests that relevant aspects of the mechanism are captured without excluding other mechanisms that might be at play in parallel as well. At very low charging currents, both experiments and modelling reveal a decrease in the amount of carbon dioxide captured, suggesting the presence of competing processes at the two electrodes, and that SSA is an inherently kinetic phenomenon. This study highlights the importance of the operating conditions of these devices and may aid their development in the future.

中文翻译：

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了解超电容摆动吸附电化学捕获 CO2 的机理


二氧化碳捕获是一系列有助于缓解气候变化的重要技术的基础。由电化学驱动的改进碳捕获技术正在积极开发中，最近发现超级电容器储能器件可以可逆地捕获和释放二氧化碳。与传统的二氧化碳捕获技术相比，所谓的超电容摆动吸附 （SSA） 具有多项优势，例如能耗更低和使用无毒材料。然而，人们对这些设备中捕获 CO2 的机制知之甚少，这使得设计改进的系统具有挑战性。在这里，通过使用 COMSOL 对水连续体输运方程进行有限元建模来研究 SSA 的机制，该方程与 CO2 到碳酸氢盐反应耦合。这个简单的计算模型再现了关键的实验观察结果，并表明充电会导致碳酸氢盐在电极中耗尽（或积累），从而驱动 CO2 在气体暴露的电极上捕获（或释放）。这表明该机制的相关方面被捕获，而不排除可能同时发挥作用的其他机制。在非常低的充电电流下，实验和建模都显示捕获的二氧化碳量减少，这表明两个电极存在竞争过程，并且 SSA 本质上是一种动力学现象。这项研究强调了这些设备工作条件的重要性，并可能有助于它们未来的发展。