Infrared study of CO adsorption on reduced and oxidised silica-supported copper catalysts

Abstract

FTIR spectra are reported of CO adsorbed on silica-supported copper catalysts prepared from copper(II) acetate monohydrate. Fully oxidised catalyst gave bands due to CO on CuO, isolated Cu²⁺ cations on silica and anion vacancy sites in CuO. The highly dispersed CuO aggregated on reduction to metal particles which gave bands due to adsorbed CO characteristic of both low-index exposed planes and stepped sites on high-index planes. Partial surface oxidation with N₂O or H₂O generated Cu⁺ adsorption sites which were slowly reduced to Cu° by CO at 300 K. Surface carbonate initially formed from CO was also slowly depleted with time with the generation of CO₂. The results are consistent with adsorbed carbonate being an intermediate in the water-gas shift reaction of H₂O and CO to H₂ and CO₂.