Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.
Nat Commun. 2019 Feb 4;10(1):573. doi: 10.1038/s41467-019-08494-6.
Aqueous precipitation of transition metal oxides often proceeds through non-equilibrium phases, whose appearance cannot be anticipated from traditional phase diagrams. Without a precise understanding of which metastable phases form, or their lifetimes, targeted synthesis of specific metal oxides can become a trial-and-error process. Here, we construct a theoretical framework to reveal the nanoscale and metastable energy landscapes of Pourbaix (E-pH) diagrams, providing quantitative insights into the size-dependent thermodynamics of metastable oxide nucleation and growth in water. By combining this framework with classical nucleation theory, we interrogate how solution conditions influence the multistage oxidation pathways of manganese oxides. We calculate that even within the same stability region of a Pourbaix diagram, subtle variations in pH and redox potential can redirect a non-equilibrium crystallization pathway through different metastable intermediates. Our theoretical framework offers a predictive platform to navigate through the thermodynamic and kinetic energy landscape towards the rational synthesis of target materials.
过渡金属氧化物的水相沉淀通常通过非平衡相进行，其出现无法从传统相图中预测。如果没有精确了解形成的亚稳相或其寿命，那么有针对性地合成特定的金属氧化物可能会成为反复试验的过程。在这里，我们构建了一个理论框架来揭示 Pourbaix（E-pH）图的纳米级和亚稳能量景观，提供了对水中亚稳氧化物成核和生长的尺寸依赖性热力学的定量见解。通过将该框架与经典成核理论相结合，我们研究了溶液条件如何影响锰氧化物的多阶段氧化途径。我们计算出，即使在 Pourbaix 图的同一稳定区域内，pH 值和氧化还原电位的微小变化也可以通过不同的亚稳中间体重新引导非平衡结晶途径。我们的理论框架提供了一个预测平台，可在热力学和动能景观中进行导航，以实现目标材料的合理合成。
