Torayev Amangeldi, Sperrin Luke, Gomez Maria A, Kattirtzi John A, Merlet Céline, Grey Clare P
Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom.
Department of Chemistry, Mount Holyoke College, South Hadley, Massachusetts 01075, United States.
J Phys Chem C Nanomater Interfaces. 2020 Jul 30;124(30):16689-16701. doi: 10.1021/acs.jpcc.0c04594. Epub 2020 Jun 23.
Y-doped BaZrO is a promising proton conductor for intermediate temperature solid oxide fuel cells. In this work, a combination of static DFT calculations and DFT based molecular dynamics (DFT-MD) was used to study proton conduction in this material. Geometry optimizations of 100 structures with a 12.5% dopant concentration allowed us to identify a clear correlation between the bending of the metal-oxygen-metal angle and the energies of the simulated cells. Depending on the type of bending, two configurations, designated as inward bending and outward bending, were defined. The results demonstrate that a larger bending decreases the energy and that the lowest energies are observed for structures combining inward bending with protons being close to the dopant atoms. These lowest energy structures are the ones with the strongest hydrogen bonds. DFT-MD simulations in cells with different yttrium distributions provide complementary microscopic information on proton diffusion as they capture the dynamic distortions of the lattice caused by thermal motion. A careful analysis of the proton jumps between different environments confirmed that the inward and outward bending states are relevant for the understanding of proton diffusion. Indeed, intra-octahedral jumps were shown to only occur starting from an outward configuration while the inward configuration seems to favor rotations around the oxygen. On average, in the DFT-MD simulations, the hydrogen bond lengths are shorter for the outward configuration which facilitates the intra-octahedral jumps. Diffusion coefficients and activation energies were also determined and compared to previous theoretical and experimental data, showing a good agreement with previous data measuring local proton motion.
钇掺杂的BaZrO是一种有前景的用于中温固体氧化物燃料电池的质子导体。在这项工作中，结合静态密度泛函理论（DFT）计算和基于DFT的分子动力学（DFT-MD）来研究该材料中的质子传导。对掺杂浓度为12.5%的100种结构进行几何优化，使我们能够确定金属-氧-金属角的弯曲与模拟电池能量之间的明确关联。根据弯曲类型，定义了两种构型，即向内弯曲和向外弯曲。结果表明，更大的弯曲会降低能量，并且对于向内弯曲且质子靠近掺杂原子的结构，观察到最低能量。这些最低能量结构是氢键最强的结构。在具有不同钇分布的电池中进行DFT-MD模拟，提供了关于质子扩散的补充微观信息，因为它们捕捉了由热运动引起的晶格动态畸变。对不同环境之间质子跳跃的仔细分析证实，向内和向外弯曲状态与理解质子扩散相关。实际上，八面体内跳跃仅从向外构型开始发生，而向内构型似乎有利于围绕氧的旋转。平均而言，在DFT-MD模拟中，向外构型的氢键长度较短，这有利于八面体内跳跃。还确定了扩散系数和活化能，并与先前的理论和实验数据进行比较，结果表明与先前测量局部质子运动的数据吻合良好。
