Synergistic Effects of Complex Cu Species in Cu–MgO Catalysts for the Water Gas Shift Reaction

The structures of active components in practical solid catalysts are seldom homogeneous, which makes it challenging to explore the synergistic effect among the complex catalyst components in heterogeneous catalysis. The active structure of Cu-based catalysts, which are widely used in water gas shift reactions and other important industrial reactions, has been debated. This work prepared Cu–MgO catalysts with the copresence of Cu particles and Cu atoms to investigate the synergistic effects of these Cu species. We found that the Cu nanoparticles served to adsorb and activate the reactant molecule of CO, while the atomic Cu species at the surface of the MgO lattice might exist as the Mg2Cu2–Ov site for water dissociation. The presence of surface-substituted Cu atoms modulated the reactivity of adjacent oxygen vacancy in the MgO surface, enhanced the ability of H2O dissociation to form reactive –OH species, and allowed the oxygen vacancies to recycle, contributing to the continuation of the reaction. A volcano-type relation of catalytic performance versus Cu0/Cu2+ ratio has been established, revealing the existence of synergy between Cu particles and Cu atoms. In addition, due to this synergistic effect, the optimized Cu–MgO catalyst shows a very high activity with a CO conversion rate of 1119 μmolCO gCu–1 s–1 at 300 °C. This work revealed the synergistic effect of different Cu species in the Cu–MgO catalysts, which was important for unraveling the contribution of complex components to catalytic performance.