Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany.
J Am Chem Soc. 2012 Jul 18;134(28):11380-3. doi: 10.1021/ja304497n. Epub 2012 Jul 3.
The ability of Mo (Cr) impurities in a CaO (MgO) matrix to act as charge donors to adsorbed gold has been investigated by means of scanning tunneling microscopy and density functional theory. Whereas CaO(Mo) features a robust donor characteristic, as deduced from a charge-transfer-driven crossover in the Au particles' geometry in the presence of dopants, MgO(Cr) is electrically inactive. The superior performance of the CaO(Mo) system is explained by the ability of the Mo ions to evolve from a +2 oxidation state in ideal CaO to a +5 state by transferring up to three electrons to the Au adislands. Cr ions in MgO, on the other hand, are stable only in the +2 and +3 charge states and can provide a single electron at best. Since this electron is likely to be captured by cationic vacancies or morphological defects in the real oxide, no charge transfer to Au particles takes place in this case. On the basis of our findings, we have developed general rules on how to optimize the electron donor characteristics of doped oxide materials.
通过扫描隧道显微镜和密度泛函理论研究了 CaO（MgO）基质中 Mo（Cr）杂质作为吸附金的荷电供体的能力。由于 CaO（Mo）具有很强的供体特性，这可以从存在掺杂剂时金颗粒几何形状的电荷转移驱动交叉推断得出，而 MgO（Cr）则是电惰性的。CaO（Mo）体系性能优越的原因是 Mo 离子能够从理想 CaO 中的+2 氧化态通过向 Au 吸附岛转移多达三个电子转变为+5 态。另一方面，MgO 中的 Cr 离子仅在+2 和+3 价态下稳定，最多只能提供一个电子。由于该电子很可能被阳离子空位或实际氧化物中的形态缺陷捕获，因此在这种情况下不会向 Au 颗粒发生电荷转移。基于我们的发现，我们制定了关于如何优化掺杂氧化物材料的电子供体特性的一般规则。
