过渡金属原子在金红石TiO2（110）表面上的路径：Ti3 +态的分布和外围电荷积累增强的证据
Transition Metal Atoms Pathways on Rutile TiO2 (110) Surface: Distribution of Ti3+ States and Evidence of Enhanced Peripheral Charge Accumulation
摘要：
金属纳米颗粒和负载型TiO 2表面之间的电荷转移对于催化应用是非常重要的，因为它极大地影响了沉积在表面上的纳米颗粒的催化活性和热稳定性。在此，进行系统的自旋极化密度泛函计算来评估几种过渡金属单体在化学计量和还原的金红石TiO 2（110）表面上的吸附、扩散和电荷状态。研究了氧空位及其伴随的过量电子在影响单体活化中的作用。对于原始的还原表面，我们的混合泛函计算表明，只有一小部分（约5%）的多余电子占据最顶部的表面，这主要是离域在第二个最近和第三个最近的五次协调Ti（Ti5c）原子。少量的过量电子填充在Ti5c原子可以转移到强电负性的吸附物，如Au和Pt，从而使适度的吸附，而没有稳定的吸附在Ti5c网站被发现为其他电负性较低的TM吸附原子（Ag，Cu，Fe，Co，Ni和Pd）的还原表面上和化学计量表面上的所有吸附原子。这一发现澄清了O2和CO分子在Ti5c位点的吸附与电荷转移的实验观察的起源。此外，在Ov周围的Ti5c网站上的过剩电子的空间重新分配的单体吸附后，彻底检查。我们的发现在单体周围的Ti5c位点处的过量电子的积累解释了沉积的纳米颗粒的周边界面在促进实验中观察到的反应物的吸附和活化中的关键作用。
英文摘要：
Charge transfer between metal nanoparticles and the supported TiO2 surface is primarily important for catalytic applications as it greatly affects the catalytic activity and the thermal stability of the deposited nanoparticles on the surface. Herein, a systematic spin-polarized density functional calculation is performed to evaluate the adsorption, diffusion, and charge state of several transition metal monomers on both stoichiometric and reduced rutile TiO2 (110) surface. The role of oxygen vacancy (Ov) with its accompanying excess electrons in influencing the activation of the monomers is examined. For pristine reduced surface, our hybrid functional calculation shows that only a small portion (around 5%) of the excess electrons occupy the topmost surface, which are mainly delocalized at the second nearest and third nearest fivefold coordinated Ti (Ti5c) atoms. The small amounts of excess electrons populating at the Ti5c atoms can be transferred to strongly electronegative adsorbates like Au and Pt thus enabling a moderate adsorption, whereas no stable adsorption at the Ti5c site is found for other less electronegative TM adatoms(Ag, Cu, Fe, Co, Ni and Pd) on the reduced surface and for all the adatoms on stoichiometric surface. This finding clarify the origin of the experimental observation of the adsorption of O2 and CO molecules at Ti5c sites in connection with charge transfer. In addition, the spatial redistribution of the excess electrons at Ti5c sites around the Ov upon the adsorption of the monomers is thoroughly examined. Our finding of an accumulation of excess electrons at the Ti5c sites around the monomers explains the critical role of the perimeter interface of the deposited nanoparticles in promoting the adsorption and activation of reactants observed in experiments.
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