Effect of active sites for a water-gas shift reaction on Cu nanoparticles

摘要

The effect on the water-gas shift reaction of active sites on Cu nanoparticles on silica prepared by atomic layer epitaxy was investigated. The Cu nanoparticles are proposed to contain two major active sites on the surface, defect sites on Cu particles (L_1 sites) and sites having strong interactions with oxide support on highly dispersed and/or isolated Cu particles (L_2 sites). The defect sites on the Cu nanoparticles induce intense dissociation of H_2O to form atomic oxygen, leading to the redox mechanism that occurred in the reaction. The atomic oxygen generated from H _2O on the defect sites has a high reactivity toward CO adsorbed onto L_1 and L_2 sites to form CO_2. The adsorption heats of CO adsorbed onto the L_1 and L_2 sites varying with coverage are obtained for coverage 0 and 1 with E_0 = 51 and E _1 = 39 kJ/mol for L_1-CO and E_0 = 70 and E _1 = 46 kJ/mol for L_2-CO.