アルカリ土類金属酸化物の配位不飽和性と吸着・触媒作用

抄録

Sucface levels and surface properties such as adsorptive and catalytic abilities of alkaline earth metal oxides strongly depend on coordinative unsaturation of intrinsic surface ions. Both theoretical and experimental works reveal the formation of two surface levels due to Mg_LC²⁺ and O_LC^2-, respectively, where LC denotes low coordination, within the bulk band gap. The surface levels originating from O_LC^2- go up with lowering of its coordination number and act as electron donative and basic centers. In many cases adsorptions and catalytic reactions proceed on dual active sites of Mg_LC²⁺-O_LC^2- types which can heterolytically dissociate molecules. Another type of adsorption is also possible on the O_LC^2- site which donates its electron to adsorbed molecules with high electron affinity. Cooperative role of Mg_LC²⁺ is also necessary in this case. Coordination numbers have been tentatively assigned to these active sites.