Modelling the chemistry of Mn-doped MgO for bulk and (100) surfaces

被引:12
|
作者
Logsdail, Andrew J. [1 ,2 ]
Downing, Christopher A. [1 ,3 ]
Keal, Thomas W. [3 ]
Sherwood, Paul [3 ]
Sokol, Alexey A. [1 ]
Catlow, C. Richard A. [1 ,2 ,4 ]
机构
[1] UCL, Dept Chem, Kathleen Lonsdale Mat Chem, 20 Gordon St, London WC1H 0AJ, England
[2] Cardiff Univ, Cardiff Catalysis Inst, Sch Chem, Cardiff CF10 3AT, S Glam, Wales
[3] STFC Daresbury Lab, Dept Comp Sci, Warrington WA4 4AD, Cheshire, England
[4] Rutherford Appleton Lab, Sci & Technol Facil Council, UK Catalysis Hub, Res Complex Harwell, Harwell Sci & Innovat Campus, Didcot OX11 0QX, Oxon, England
基金
英国工程与自然科学研究理事会; 英国科学技术设施理事会;
关键词
AB-INITIO CALCULATIONS; OXIDE SURFACES; OXYGEN VACANCY; ELECTRONIC-STRUCTURE; MGO(100) SURFACE; SOLID-SOLUTIONS; DENSITY; QM/MM; CO2; TRANSITION;
D O I
10.1039/c6cp04622c
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
We have investigated the energetic properties of Mn-doped MgO bulk and (100) surfaces using a QM/MM embedding computational method, calculating the formation energy for doped systems, as well as for surface defects, and the subsequent effect on chemical reactivity. Low-concentration Mn doping is endothermic for isovalent species in the bulk but exothermic for higher oxidation states under p-type conditions, and compensated by electrons going to the Fermi level rather than cation vacancies. The highest occupied dopant Mn 3d states are positioned in the MgO band gap, about 4.2 eV below the vacuum level. Surface Mn-doping is more favourable than subsurface doping, and marginally exothermic on a (100) surface at high O-2 pressures. For both types of isovalent Mn-doped (100) surfaces, the formation energy for catalytically important oxygen defects is less than for pristine MgO, with F-0 and F2+-centres favoured in n- and p-type conditions, respectively. In addition, F+-centres are stabilised by favourable exchange coupling between the Mn 3d states and the vacancy-localised electrons, as verified through calculation of the vertical ionisation potential. The adsorption of CO2 on to the pristine and defective (100) surface is used as a probe of chemical reactivity, with isovalent subsurface Mn dopants mildly affecting reactivity, whereas isovalent surface-positioned Mn strongly alters the chemical interactions between the substrate and adsorbate. The differing chemical reactivity, when compared to pristine MgO, justifies further detailed investigations for more varied oxidation states and dopant species.
引用
收藏
页码:28648 / 28660
页数:13
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