Ghosh Sukanya, Mammen Nisha, Narasimhan Shobhana
Theoretical Sciences Unit and School of Advanced Materials, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560064, India.
J Chem Phys. 2020 Apr 14;152(14):144704. doi: 10.1063/1.5143642.
We show, using density functional theory calculations, that the charge, magnetic moment, and morphology of deposited Au nanoclusters can be tuned widely by doping the oxide support with aliovalent cations and anions. As model systems, we have considered Au (n = 1, 2, or 20) deposited on doped MgO and MgO/Mo supports. The supports have been substitutionally doped with varying concentrations θ of F, Al, N, Na, or Li. At θ = 2.78%, by varying the dopant species, we are able to tune the charge of the Au monomer between -0.84e and +0.21e, the Au dimer between -0.87e and -0.16e, and, most interestingly, Au between -3.97e and +0.49e. These ranges can be further extended by varying θ. These changes in charge are correlated with changes in adsorption and/or cluster geometry and magnetic moment. We find that the work function Φ of the bare support is a good predictor and descriptor of both the geometry and charge of the deposited Au cluster; it can, therefore, be used to quickly estimate which dopant species and concentration can result in a desired cluster morphology and charge state. This is of interest as these parameters are known to significantly impact cluster reactivity, with positively or negatively charged clusters being preferred as catalysts for different chemical reactions. It is particularly noteworthy that the Na-doped and Li-doped supports succeed in making Au positively charged, given the high electronegativity of Au.
我们通过密度泛函理论计算表明，通过用异价阳离子和阴离子掺杂氧化物载体，可以广泛调节沉积的金纳米团簇的电荷、磁矩和形态。作为模型系统，我们考虑了沉积在掺杂的氧化镁和氧化镁/钼载体上的金（n = 1、2或20）。载体已被不同浓度θ的氟、铝、氮、钠或锂进行了替代掺杂。在θ = 2.78%时，通过改变掺杂剂种类，我们能够将金单体的电荷调节在-0.84e至+0.21e之间，金二聚体的电荷调节在-0.87e至-0.16e之间，最有趣的是，将金团簇的电荷调节在-3.97e至+0.49e之间。这些范围可以通过改变θ进一步扩展。电荷的这些变化与吸附和/或团簇几何形状及磁矩的变化相关。我们发现，裸载体的功函数Φ是沉积的金团簇几何形状和电荷的良好预测指标和描述符；因此，它可用于快速估计哪种掺杂剂种类和浓度能够导致所需的团簇形态和电荷状态。这一点很重要，因为已知这些参数会显著影响团簇的反应活性，带正电荷或负电荷的团簇分别作为不同化学反应的催化剂更受青睐。特别值得注意的是，鉴于金的高电负性，钠掺杂和锂掺杂的载体成功地使金带正电荷。
