Imtiaz Qasim, Armutlulu Andac, Donat Felix, Müller Christoph
Laboratory of Energy Science and Engineering, Department of Mechanical and Process Engineering, ETH Zürich, 8092 Zurich, Switzerland.
Present Address: Department of Chemistry and Chemical Engineering, Lahore University of Management Sciences, Lahore, 54792 Pakistan.
Discov Chem Eng. 2022;2(1):6. doi: 10.1007/s43938-022-00013-2. Epub 2022 Oct 26.
Thermochemical redox cycles such as chemical looping combustion (CLC) are an economically promising CO capture technology that rely on the combustion of a hydrocarbon fuel with lattice oxygen that is derived from a solid oxygen carrier. The oxygen carrier is typically regenerated with air. To increase the agglomeration resistance and redox stability of the oxygen carriers, the active phase is often stabilized with high Tammann temperature ceramics, resulting in the formation of so-called cermet structures. It has been hypothesized that the redox performance of the cermets depends critically on the conduction pathways for solid-state ionic diffusion and the activation energy for charge transport. Here, we investigate the influence of the formation of a percolation network on the electrical conductivity and the rate of oxidation for CeO-stabilized Cu. We found that for oxygen carriers that contained 60 wt. % CuO, the charge transport occurred predominately via Cu/CuO conduction pathways. Below the percolation threshold of CuO, the conduction of charge carriers took place via CeO grains, which formed a continuous network. The measurements of charge transport and redox characteristics confirmed that the activation energy for charge transport through the cermet increased with decreasing Cu content. This indicates that the solid-state diffusion of charge carriers plays an important role during re-oxidation.
The online version contains supplementary material available at 10.1007/s43938-022-00013-2.
热化学氧化还原循环，如化学链燃烧（CLC），是一种在经济上有前景的二氧化碳捕集技术，它依赖于烃类燃料与源自固体氧载体的晶格氧的燃烧。氧载体通常用空气再生。为了提高氧载体的抗团聚性和氧化还原稳定性，活性相通常用高坦曼温度陶瓷来稳定，从而形成所谓的金属陶瓷结构。据推测，金属陶瓷的氧化还原性能关键取决于固态离子扩散的传导途径和电荷传输的活化能。在此，我们研究了渗流网络的形成对CeO稳定的Cu的电导率和氧化速率的影响。我们发现，对于含60 wt.% CuO的氧载体，电荷传输主要通过Cu/CuO传导途径发生。在CuO的渗流阈值以下，电荷载流子的传导通过形成连续网络的CeO晶粒进行。电荷传输和氧化还原特性的测量证实，通过金属陶瓷的电荷传输活化能随Cu含量的降低而增加。这表明电荷载流子的固态扩散在再氧化过程中起重要作用。
在线版本包含可在10.1007/s43938-022-00013-2获取的补充材料。
