Yaghoobnejad Asl Hooman, Manthiram Arumugam
Materials Science and Engineering Program and Texas Materials Institute, University of Texas at Austin, Austin, Texas 78712, United States.
J Am Chem Soc. 2020 Dec 16;142(50):21122-21130. doi: 10.1021/jacs.0c10044. Epub 2020 Dec 7.
The interfacial chemical reactivity of Jahn-Teller-active transition-metal oxides remains an enigmatic area, often leading to uncontrollable phase transformations in the oxide-based technological applications. In particular, the higher tendency of unwanted transition-metal-ion dissolution and side-reactions in Jahn-Teller-active oxides is accompanied by performance degradation in many electrochemical systems, for example, lithium-ion batteries. We show here that the fundamental electronic structure instability that leads to Jahn-Teller (lattice) distortion in an octahedral ligand field is the active chemical driving force for the spontaneous disproportionation, phase transformation, and metal-ion dissolution in transition-metal oxides upon exposure to protons. On the basis of electronic structure analyses and O isotope labeling, we present a mechanism comprising a coupled acid-base/redox reaction that leads to a proton-induced disproportionation of Jahn-Teller-active transition-metal ions, as exemplified by the broad classes of respective oxides.
Jahn-Teller 活性过渡金属氧化物的界面化学反应性仍是一个神秘的领域，这常常导致基于氧化物的技术应用中出现无法控制的相变。特别是，Jahn-Teller 活性氧化物中过渡金属离子不必要的溶解和副反应的倾向较高，这在许多电化学系统（例如锂离子电池）中伴随着性能下降。我们在此表明，在八面体配体场中导致 Jahn-Teller（晶格）畸变的基本电子结构不稳定性是过渡金属氧化物在暴露于质子时自发歧化、相变和金属离子溶解的活性化学驱动力。基于电子结构分析和 O 同位素标记，我们提出了一种包含耦合酸碱/氧化还原反应的机制，该机制导致质子诱导的 Jahn-Teller 活性过渡金属离子歧化，各类相应氧化物均有体现。
