Enhanced oxygen mobility of nonreducible MgO-supported Cu catalyst by defect engineering for improving the water-gas shift reaction

Understanding how to tune the properties of metal oxides is essential for developing metal oxide-supported catalysts with enhanced activity. Here, nonreducible MgO-supported Cu (MgCu) catalysts were prepared by varying the content of MgO. The rate of the water–gas shift reaction over the MgCu50 catalyst was 70 μmol CO g⁻¹s⁻¹ at 300 °C, which is twice that achieved with reported metal oxide-supported catalysts. The limited reducibility of MgO was overcome by introducing abundant defects by effectively replacing Mg²⁺ with Cu²⁺, which resulted in significant changes in the electron density of MgO. CO-pulse titration experiments proved that the defect-rich MgO-supported catalyst exhibited highly enhanced activity toward CO due to abundant active oxygen species on the surface. The reconstruction of active surface oxygen in MgO was markedly promoted in the catalysts with higher MgO content, as well as at higher temperatures. This study demonstrates the feasibility of utilizing nonreducible MgO as an active support for reactions where redox properties are important.