Differentiating the Reactivity of ZrO₂-Bound Formates Formed on Cu/ZrO₂ during CO₂ Hydrogenation

The surface species formed during the hydrogenation of CO2 with H2 over a ZrO2-supported Cu catalyst were investigated by operando diffuse reflectance FT-IR spectroscopy at 220 °C and 3 bar. The reactivity of two different formates located on zirconia could be unraveled. The data pointed to ZrO2 hydroxyl groups at 3755 cm−1 as the sites on which carbonates and then formates were hydrogenated to methoxy species. Formate hydrogenation appeared as the slowest step. The most reactive ZrO2-bound formates exhibited a rate constant of reaction about 65 times higher than that of the slower formate.