High-pressure in situ X-ray absorption fine structure measurements for hydrogenation of CO2 to methanol over Zn-doped ZrO2

Abstract

Obtaining insights into the active-site structure of a catalyst during high-pressure and high-temperature catalytic reactions is extremely challenging. In this study, changes in the coordination structure of Zn species in Zn-doped ZrO₂ catalysts (Zn/(Zn + Zr) atomic ratio = 9%) during CO₂-to-methanol hydrogenation (cell temperature = 400 °C, pressure = 9 bars) was investigated using high-pressure in situ X-ray absorption fine structure measurements and density functional theory calculations. The formation of Zn–H species, which are considered the active sites for the reaction, was very limited, with most Zn species existing as [ZnO_a] isolated clusters. Additionally, the adsorption of CO₂ at the Zr⁴⁺ sites near the Zn species induced significant distortions in the coordination structure of the Zn species. This study provides new insights into the catalytic active-site structure.