Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Department of Chemistry, Fudan University, Shanghai 200433, China.
J Am Chem Soc. 2011 Oct 5;133(39):15743-52. doi: 10.1021/ja206153v. Epub 2011 Sep 9.
TiO(2) nanoparticles have been widely utilized in photocatalysis, but the atomic level understanding on their working mechanism falls much short of expectations. In particular, the correlation between the particle structure and the photocatalytic activity is not established yet, although it was observed that the activity is sensitive to the particle size and shape. This work, by investigating a series of TiO(2) anatase nanoparticles with different size and shape as the photocatalyst for water oxidation, correlates quantitatively the particle size and shape with the photocatalytic activity of the oxygen evolution reaction (OER). Extensive density functional theory (DFT) calculations combined with the periodic continuum solvation model have been utilized to compute the electronic structure of nanoparticles in aqueous solution and provide the reaction energetics for the key elementary reaction. We demonstrate that the equilibrium shape of nanoparticle is sensitive to its size from 1 to 30 nm, and the sharp crystals possess much higher activity than the flat crystals in OER, which in combination lead to the morphology dependence of photocatalytic activity. The conventionally regarded quantum size effect is excluded as the major cause. The physical origin for the shape-activity relationship is identified to be the unique spatial separation/localization of the frontier orbitals in the sharp nanoparticles, which benefits the adsorption of the key reaction intermediate (i.e., OH) in OER on the exposed five-coordinated Ti of {101} facet. The theoretical results here provide a firm basis for maximizing photocatalytic activity via nanostructure engineering and are also of significance for understanding photocatalysis on nanomaterials in general.
TiO(2) 纳米粒子在光催化中得到了广泛的应用，但对其工作机制的原子水平理解还远远不够。特别是，尽管已经观察到活性对颗粒尺寸和形状敏感，但颗粒结构与光催化活性之间的相关性尚未建立。在这项工作中，通过研究一系列具有不同尺寸和形状的 TiO(2)锐钛矿纳米粒子作为水氧化的光催化剂，我们定量地将颗粒尺寸和形状与析氧反应（OER）的光催化活性相关联。我们利用广泛的密度泛函理论（DFT）计算结合周期性连续体溶剂化模型，计算了纳米粒子在水溶液中的电子结构，并为关键基元反应提供了反应能学。我们证明，纳米粒子的平衡形状对其尺寸从 1 到 30nm 是敏感的，并且在 OER 中锐晶比扁平晶具有更高的活性，这两者共同导致了光催化活性的形态依赖性。传统上认为的量子尺寸效应被排除为主要原因。形状-活性关系的物理起源被确定为在锐晶纳米粒子中前沿轨道的独特空间分离/定位，这有利于关键反应中间体（即 OH）在 OER 中吸附在暴露的{101}面的五配位 Ti 上。这里的理论结果为通过纳米结构工程最大化光催化活性提供了坚实的基础，对理解纳米材料的光催化也具有重要意义。
