Emhjellen Linn Katinka, Thoréton Vincent, Xing Wen, Haugsrud Reidar
Department of Chemistry, Centre for Materials Science and Nanotechnology, University of Oslo, FERMiO, Gaustadalléen 21, NO-0349 Oslo, Norway.
SINTEF Industry, Sustainable Energy Technology, Pb. 124 Blindern, NO-0314 Oslo, Norway.
ACS Phys Chem Au. 2025 Feb 11;5(2):239-248. doi: 10.1021/acsphyschemau.4c00111. eCollection 2025 Mar 26.
The kinetics of oxygen exchange dictate the rate of redox reactions, which is crucial for electrochemical-based sustainable technologies. In this study, we use isotope exchange pulse responses to elucidate the oxygen exchange mechanism for (BiTm)O (BTM)-(LaSr)MnO (LSM) composites. With an optimized composition and microstructure, these composites can achieve polarization resistances below 0.01 Ω·cm at 700 °C. Analysis of the oxygen exchange rate, , by splitting it into elementary processes using the serial two-step scheme, demonstrates that both the dissociative adsorption and incorporation of oxygen are accelerated in BTM-LSM compared to the parent phases. Dissociative adsorption of molecular oxygen is rate-limiting below 900 °C in the range 0.002-0.05 atm O and below 850 °C in 0.21 atm O. Cation interdiffusion or changes in the electronic structure at the interface between the two materials create an electrocatalytically active region spanning 1-40 nm around the BTM-LSM phase boundary. Oxygen exchange coefficients within this region were estimated to be 2-3 orders of magnitude higher compared to those of the entire composite surface. We propose two potential pathways for oxygen exchange in BTM-LSM, with calculated dependencies for each rate-determining step (). The dependency of reveals that molecular oxygen is involved in the .
氧交换动力学决定了氧化还原反应的速率，这对于基于电化学的可持续技术至关重要。在本研究中，我们使用同位素交换脉冲响应来阐明（BiTm）O（BTM）-（LaSr）MnO（LSM）复合材料的氧交换机制。通过优化的组成和微观结构，这些复合材料在700°C时可实现低于0.01Ω·cm的极化电阻。使用串联两步法将氧交换速率分解为基本过程进行分析，结果表明，与母体相相比，BTM-LSM中氧的解离吸附和掺入均得到加速。在0.002 - 0.05 atm O₂条件下，低于900°C时，分子氧的解离吸附是限速步骤；在0.21 atm O₂条件下，低于850°C时，分子氧的解离吸附是限速步骤。两种材料界面处的阳离子相互扩散或电子结构变化在BTM-LSM相界周围形成了一个1 - 40 nm的电催化活性区域。该区域内的氧交换系数估计比整个复合材料表面的氧交换系数高2 - 3个数量级。我们提出了BTM-LSM中氧交换的两条潜在途径，并计算了每个速率决定步骤（）的 依赖性。 的依赖性表明分子氧参与了 。
