Hai Pengqi, Wu Chao
Frontier Institute of Science and Technology, Xi'an Jiaotong University, Xi'an 710049, China.
Phys Chem Chem Phys. 2021 Oct 27;23(41):24004-24015. doi: 10.1039/d1cp03241k.
The thermodynamic and kinetic behaviors of O atoms on and in different Al nanoparticles (ANPs) and Al crystals have been systematically studied using first-principles calculations. The O adsorption strength on clean Al surfaces follows the order of (111) > ANPs > (110) > (100). The O adsorption strength on ANPs approaches that on Al(111) as the cluster size increases. The three-fold fcc-like sites on ANPs rather than the corner and edge sites are more favored by O* adatoms, which is due to the larger deformation energy related to the geometry change of ANPs when O is adsorbed at the corner and edge sites. The O adsorption behaviors on ANPs are different both from previous studies based on reactive force fields (ReaxFFs) and from those on transition metal clusters. The effective O-O interaction is short ranged (<5 Å), isotropic (in-plane and across-layer) and attractive over different Al surfaces and subsurfaces. The attraction is always about -0.1 eV per O pair at the first nearest neighboring (1NN) sites unless there is evident surface curvature or restructure. Due to the universal attraction, the O* adatoms either on the surface or in the subsurfaces prefer to form islands. In addition, any O diffusion away from the O islands will experience a much higher energy barrier than on a clear (sub)surface. Besides the most stable (AlO) fragments, the metastable Al oxidation fragments are AlO monomers and (AlO) oligomers, which may be formed during intense oxidation and all feature tetra-coordinated Al and bi-coordinated O atoms.
利用第一性原理计算系统研究了O原子在不同铝纳米颗粒（ANPs）和铝晶体上及内部的热力学和动力学行为。清洁铝表面上的O吸附强度顺序为(111)＞ANPs＞(110)＞(100)。随着团簇尺寸增加，ANPs上的O吸附强度接近Al(111)上的吸附强度。ANPs上的面心立方（fcc）类三重位点比边角位点更受O吸附原子青睐，这是因为当O吸附在边角位点时，与ANPs几何形状变化相关的变形能更大。ANPs上的O吸附行为既不同于以往基于反应力场（ReaxFFs）的研究，也不同于过渡金属团簇上的吸附行为。有效的O - O相互作用范围较短（<5 Å），具有各向同性（面内和面间），且在不同铝表面和次表面上具有吸引力。在第一近邻（1NN）位点，每对O的吸引力通常约为 -0.1 eV，除非存在明显的表面曲率或重构。由于普遍存在的吸引力，表面或次表面上的O吸附原子都倾向于形成岛状结构。此外，任何O从O岛扩散离开时所经历的能垒都比在清洁（次）表面上高得多。除了最稳定的(AlO)片段外，亚稳的铝氧化片段是AlO单体和(AlO)低聚物，它们可能在剧烈氧化过程中形成，且都具有四配位的Al原子和双配位的O原子。
