Koleva Iskra Z, Aleksandrov Hristiyan A, Neyman Konstantin M, Vayssilov Georgi N
Faculty of Chemistry and Pharmacy, University of Sofia, 1126 Sofia, Bulgaria.
Phys Chem Chem Phys. 2020 Nov 25;22(45):26568-26582. doi: 10.1039/d0cp05456a.
Structural properties and reducibility of zirconium-doped cerium dioxide systems were studied using periodic plane-wave calculations based on density functional theory. A systematic analysis of the results for nanoparticles of two sizes, Ce40-nZrnO80 ∼ 1.5 nm large and Ce140-nZrnO280 ∼ 2.4 nm large, in comparison with slab model data for Ce1-xZrxO2(111) surface has been performed focusing on specific nanoscale effects. Several loadings of Zr dopants ranging from 0.7 to 50 atomic metal percent have been considered. Subsurface cationic sites of ceria are calculated to be energetically most favourable for doping Zr4+ ions in all models. The system stability with several zirconium ions is defined by the relative stability of the occupied individual Zr4+ positions when only one zirconium ion is present. Data for the Ce70Zr70O280 nanoparticle with an equal number of Ce4+ and Zr4+ cations reveal that atomic orderings of neither separated oxide (Janus-type) particles nor randomly intermixed ones are more stable than the distribution of Zr atoms occupying all cationic positions inside the nanoparticle to minimize the presence of surface zirconium. The basicity of surface oxygen centers in nanoparticles is predicted to be decreased when Zr dopants are located in surface positions. The presence of Zr4+ dopants in CeO2 systems can notably lower the oxygen vacancy formation energy and shows interesting peculiarities at higher Zr loadings. Among them is the higher stability of inner oxygen vacancies in Zr-containing nanoparticles and enhanced oxygen mobility beneficial for application in catalysis and as a solid electrolyte with oxygen ions as charge carriers. Similar to pure ceria, Zr-doped ceria nanoparticles exhibit notably higher reducibility than the corresponding extended systems.
基于密度泛函理论，采用周期性平面波计算方法研究了锆掺杂二氧化铈体系的结构性质和还原性能。对两种尺寸的纳米颗粒（直径约1.5 nm的Ce40 - nZrnO80和直径约2.4 nm的Ce140 - nZrnO280）的结果进行了系统分析，并与Ce1 - xZrxO2(111)表面的平板模型数据进行了比较，重点关注特定的纳米尺度效应。考虑了几种锆掺杂量，范围从0.7到50原子百分比的金属。在所有模型中，氧化铈的次表面阳离子位点在能量上被计算为最有利于Zr4 +离子的掺杂。当只存在一个锆离子时，几个锆离子体系的稳定性由占据的单个Zr4 +位置的相对稳定性定义。具有相等数量Ce4 +和Zr4 +阳离子的Ce70Zr70O280纳米颗粒的数据表明，无论是分离的氧化物（双面神型）颗粒还是随机混合的颗粒，其原子排列都不比纳米颗粒内部所有阳离子位置都被Zr原子占据以最小化表面锆存在的分布更稳定。当Zr掺杂剂位于表面位置时，预计纳米颗粒表面氧中心的碱度会降低。CeO2体系中Zr4 +掺杂剂的存在可以显著降低氧空位形成能，并且在较高Zr负载量时表现出有趣的特性。其中包括含Zr纳米颗粒内部氧空位的更高稳定性以及增强的氧迁移率，这有利于催化应用以及作为以氧离子为电荷载流子的固体电解质。与纯氧化铈类似，Zr掺杂的氧化铈纳米颗粒比相应的扩展体系表现出明显更高的还原性能。
