Li Zuoan, Larring Yngve
Sustainable Energy Technology, SINTEF, P.O. Box 124, NO-0314 Oslo, Norway.
Energy Fuels. 2024 Jul 26;38(16):15642-15651. doi: 10.1021/acs.energyfuels.4c02625. eCollection 2024 Aug 15.
The understanding and development of stable redox materials based on cheap and abundant elements, forming Ca-Mn-Ti-Fe-O-based perovskites, have been in focus for applications in renewable technologies such as chemical looping combustion and thermal energy storage. The present research focuses on developing stable materials to be utilized up to 1050 °C in a CLC process and has shown that the structure stability and oxygen transfer capacity can be achieved by tuning the content of different elements on B-sites of the perovskites. Various experiments, such as redox cycling under various fuels, temperatures, and O, were carried out to evaluate the oxygen transfer capacity, reaction rates under various fuels, etc. The redox stability at high temperatures was evaluated by redox cycles at 1050 °C followed by post SEM analyses on surface and depth profiling. The three developed materials can avoid phase change during redox due to the moderate oxygen transfer capacity of up to 5.6 wt % O for CaMnTiFeO at 1050 °C, which is important for having stable particles. Cation diffusion was also investigated during redox cycling in the development of stable redox materials, and only a minor diffusion of Mn to the grain boundaries is seen in the least stable material. The findings show that perovskites with high stability can be obtained with more Ti on B-sites, termed as CaMnTiFeO. The developed stable oxides, to some extent, have a reduced activity compared to the less stable composition with less Ti and more Mn, termed as CaMnTiFeO, which possesses a higher oxygen release to inert ca. 1.1 wt % O compared to more stable CaMnTiFeO that can release up to 0.8 wt % O. Two of the materials have faster kinetics than ilmenite by a factor of 2 in H.
基于廉价且丰富的元素开发稳定的氧化还原材料，形成钙锰钛铁氧体基钙钛矿，一直是化学链燃烧和热能存储等可再生技术应用的研究重点。目前的研究重点是开发在化学链燃烧过程中可在高达1050°C的温度下使用的稳定材料，并且已经表明，通过调整钙钛矿B位上不同元素的含量，可以实现结构稳定性和氧转移能力。进行了各种实验，如在各种燃料、温度和氧气条件下的氧化还原循环，以评估氧转移能力、各种燃料下的反应速率等。通过在1050°C下进行氧化还原循环，随后对表面和深度剖析进行扫描电子显微镜（SEM）后分析，评估了高温下的氧化还原稳定性。由于CaMnTiFeO在1050°C时高达5.6 wt% O的适度氧转移能力，所开发的三种材料在氧化还原过程中可避免相变，这对于获得稳定颗粒很重要。在稳定氧化还原材料的开发过程中，还研究了氧化还原循环过程中的阳离子扩散，在最不稳定的材料中仅观察到少量的锰扩散到晶界。研究结果表明，在B位上含有更多钛的钙钛矿（称为CaMnTiFeO）可以获得高稳定性。与含有较少钛和较多锰的较不稳定组成（称为CaMnTiFeO）相比，所开发的稳定氧化物在一定程度上活性有所降低，CaMnTiFeO向惰性物质释放的氧量较高，约为1.1 wt% O，而更稳定的CaMnTiFeO最多可释放0.8 wt% O。其中两种材料在氢气中的动力学比钛铁矿快2倍。
