Identification and reactivity of a surface intermediate in the photoreduction of CO2 with H2 over ZrO2

Abstract

Zirconium oxide is active for photoreduction of gaseous carbon dioxide to carbon monoxide with hydrogen. A stable surface species arises under the photoreduction of CO₂ on zirconium oxide and is identified as surface formate by IR spectroscopy. Adsorbed CO₂ is converted to formate by photoreaction with hydrogen. The surface formate is a true reaction intermediate since CO is formed by the photoreaction of formate and CO₂; surface formate works as a reductant of carbon dioxide to yield carbon monoxide. The dependence on the wavelength of irradiation light shows that bulk ZrO₂ is not the photoactive species. When ZrO₂ adsorbs CO₂ a new band appears in the photoluminescence excitation spectrum. The photoactive species in the reaction between CO₂+H₂ which yields HCOO^- is presumably formed by the adsorption of CO₂ on the ZrO₂ surface.