In chemical looping with oxygen uncoupling, oxygen carrier (OC) circulates between the fuel and air reactors to release and absorb O₂ repeatedly. In order to assess the re-oxidation characteristic of Cu-based OC in the air reactor from the microscopic mechanism and macroscopic kinetics perspective, DFT calculations and isothermal oxidation experiments were conducted. In DFT calculations, Cu₂O(111) surface was chosen as the objective surface to explore the oxygen uptake as well as the atomic transportation pathways, and to determine the rate-limiting steps basing on the energy barrier analyses. It was found that the energy barrier of the surface reaction step (0.96 eV) is smaller than that of the ions diffusion step (1.61 eV). Moreover, the Cu cations outward diffusion occurs more easily than O anions inward diffusion, which confirmed the epitaxial growth characteristic of Cu₂O oxidation. The isothermal oxidation experiments were conducted in a thermogravimetric analyzer (TGA), and about 3.5 mg CuO@TiO₂-Al₂O₃ particles within the diameter range of 75–110 µm were tested between 540 and 600 °C, where the internal and external gas diffusion effects were eliminated. Mixtures of 5.2-21.0 vol.% O₂ in N₂ were adopted as the gas agent for oxidation. Based on the understandings obtained from DFT calculations, a simple mathematical model with unknown parameters of the surface reaction process (mainly the activation energy, E_k) and ions diffusion process (mainly the activation energy, E_D) was established to describe the overall oxidation process in TGA experiments. Eventually, these unknown parameters were determined as E_k= 50.5 kJ/mol and E_k= 79.2 kJ/mol via global optimization. With the attained parameters, simulations reproduced the experimental results very well, which demonstrated that this simplification model, where grain is converted almost layer by layer but different from the feature of the shrinking core model is able to accurately describe the overall oxidation process of Cu₂O.

在与氧气解偶联的化学循环中，氧气载体（OC）在燃料和空气反应器之间循环，以反复释放和吸收O ₂。为了从微观机理和宏观动力学角度评估空气反应堆中铜基OC的再氧化特性，进行了DFT计算和等温氧化实验。在DFT计算中，Cu ₂选择O（111）表面作为目标表面，以研究氧的吸收以及原子的运输途径，并基于能垒分析确定限速步骤。发现表面反应步骤的能垒（0.96eV）小于离子扩散步骤的能垒（1.61eV）。此外，Cu阳离子向外扩散比O阴离子向内扩散更容易发生，这证实了Cu ₂ O氧化的外延生长特性。等温氧化实验是在热重分析仪（TGA）和约3.5 mg CuO @ TiO ₂ -Al ₂ O _{3中进行的。}在540至600°C之间测试了直径范围为75–110 µm的颗粒，消除了内部和外部气体扩散效应。在N ₂中采用5.2-21.0％（体积）O _2的混合物作为氧化气体。基于DFT计算的理解，建立了一个简单的数学模型，该模型具有未知的表面反应过程参数（主要是活化能E _k）和离子扩散过程参数（主要是活化能E _D）来描述整体氧化TGA实验中的过程。最终，这些未知参数确定为E _k= 50.5 kJ / mol和E _k通过全局优化= 79.2 kJ / mol。利用所获得的参数，模拟结果很好地再现了实验结果，表明该简化模型几乎可以逐层转换晶粒，但与收缩核模型的特征不同，该模型能够准确地描述Cu ₂的整体氧化过程。哦