Surface distributions of Li in two Li/MgO catalysts with similar Li content but different microstructures and catalytic performance in the OCM reaction were characterized by synchrotron radiation photoelectron spectroscopy. Both Li/MgO catalysts show similar Li content within the topmost surface region, while the Li/MgO catalyst with a Li surface distribution capable of maintaining the migration and desorption processes of Li during the OCM reaction exhibits MgO surfaces with microstructures active in the OCM reaction. These results demonstrate that Li in Li/MgO catalysts acts as a structural modifier of the active MgO component rather than as an active center. (C) 2016 Elsevier Inc. All rights reserved.