Jiang Yunan, Wang Shuang, Xu Jun, Zheng Minghao, Yang Yi, Wu Xiaojun, Xia Changrong
Chinese Academy of Sciences (CAS) Key Laboratory of Materials for Energy Conversion, Department of Materials Science and Engineering, University of Science and Technology of China, Hefei, China.
Department of Materials Science and Engineering, University of Science and Technology of China, Hefei, China.
Front Chem. 2021 Feb 1;8:591322. doi: 10.3389/fchem.2020.591322. eCollection 2020.
Ni-ceria cermets are potential anodes for intermediate-temperature solid oxide fuel cells, thanks to the catalytic activity and mixed conductivities of ceria-based materials associated with the variable valence states of cerium. However, the anodic reaction mechanism in the Ni-ceria systems needs to be further revealed. Via density functional theory with strong correlated correction method, this work gains insight into reaction pathways of hydrogen oxidation on a model system of Ni-CeO(111). The calculation shows that electrons tend to be transferred from Ni cluster to cerium surface, creating surface oxygen vacancies. Six pathways are proposed considering different adsorption sites, and the interface pathway proceeding with hydrogen spillover is found to be the prevailing process, which includes a high adsorption energy of -1.859 eV and an energy barrier of 0.885 eV. The density functional theory (DFT) calculation results are verified through experimental measurements including electrical conductivity relaxation and temperature programmed desorption. The contribution of interface reaction to the total hydrogen oxidation reaction reaches up to 98%, and the formation of Ni-ceria interface by infiltrating Ni to porous ceria improves the electrochemical activity by 72% at 800°C.
镍铈金属陶瓷由于铈基材料与铈的可变价态相关的催化活性和混合电导率，是中温固体氧化物燃料电池的潜在阳极。然而，镍铈体系中的阳极反应机理仍需进一步揭示。通过采用强关联校正方法的密度泛函理论，这项工作深入了解了镍 - 二氧化铈（111）模型体系上氢氧化反应的途径。计算表明，电子倾向于从镍簇转移到铈表面，产生表面氧空位。考虑不同吸附位点提出了六种途径，发现以氢溢流进行的界面途径是主要过程，其包括 -1.859 eV 的高吸附能和 0.885 eV 的能垒。通过包括电导率弛豫和程序升温脱附在内的实验测量验证了密度泛函理论（DFT）计算结果。界面反应对总氢氧化反应的贡献高达 98% , 并且通过将镍渗透到多孔二氧化铈中形成镍铈界面，在 800°C 时将电化学活性提高了 72%。
