XANES study of Li‐MgO and Li‐La 2 O 3 ‐MgO catalysts for oxidative coupling of methane

To characterize the defect sites in the near‐surface and bulk phase of Li‐MgO and Li‐La 2 O 3 ‐MgO, XANES at Mg K‐edge and La L3‐edge was applied. For Li‐MgO, it can be suggested that Li doping at a low content (2.5 wt%) brings about the formation of defect species only in the near‐surface. This is due to the localization of doped Li ions in the surface, and thus the catalytically active species containing [Li+‐O‐] type center exist in the surface region. After OCM reaction, the defect species are formed in the near‐surface over MgO and Li‐MgO. By addition of La 2 O 3 to Li‐MgO (La/(Mg+La)=0.25), the structural change during the reaction is almost suppressed in the surface. In addition, the Li‐La 2 O 3 ‐MgO shows higher C2 selectivity than Li‐MgO.