A DFT and microkinetic study of HCHO catalytic oxidation mechanism over Pd/Co3O4 catalysts: The effect of metal-oxide interface

Abstract

Abstract The oxidation of HCHO at the interface between Pd and Co3O4 support was studied by using density of functional theory (DFT) calculation. A Pd/Co3O4 model was established to investigate the complex interaction of reactants, products, and catalysts under reaction conditions. The interface interaction led to the electron migration from Pd to Co3O4, which enhanced the adsorption of HCHO and O2. Pd atoms played the role as the active sites in the whole process of HCHO oxidation. Interface interaction changed the adsorption mode of CO oxidation, which contributed to CO activation. The calculated results showed that the energy barrier of CO oxidation at Pd/Co3O4 interface was lower than that on Pd (111) surface. Barrier decomposition analysis showed CO activation determined the energy barrier difference between the interface and Pd (111) surface. Microkinetics studies indicated that CO oxidation on Pd (111) surface was the rate limiting step, and the catalyst surface was covered with CO molecules. At Pd/Co3O4 interface, CO was completely converted to CO2 and the adsorption of HCHO and O2 was the rate limiting step at low temperature. At Pd/Co3O4 interface, the production rate of CO2 and H2O was 15 times higher than that on Pd (111) surface, which indicated that Pd/Co3O4 interface could improve catalytic activity of HCHO, especially at room temperature.