The lattice oxygen determines the methanol selectivity in CO2 hydrogenation over ZnZrOx catalysts

Abstract

Methanol production from CO₂ hydrogenation is a green CO₂ utilization technology currently being pursued in the methanol economy. ZnZrO_x solid solution catalysts have been extensively explored for CO₂ hydrogenation to methanol; however, the role of oxygen species is not well established. In this work, the solid phase milling approach was employed to fabricate a series of ZnZrO_x catalysts with various ratios of vacancy oxygen to lattice oxygen. Catalyst ZZ-320 obtained at a speed of 320 r min⁻¹ had the best hydrogenation activity, achieving nearly 5.2% CO₂ conversion and 72.2% methanol selectivity at 325 °C. Catalyst ZZ-320 possessed abundant basic sites to adsorb and activate CO₂ and had rich lattice oxygen. A linear relationship between lattice oxygen concentration and methanol selectivity was identified, indicating the key role of lattice oxygen in CO₂ hydrogenation to methanol. The mechanism study showed that both HCOO* and CH₃O* were the reactive intermediates. This study contributes to a deeper systematic understanding of the effect of catalyst oxygen distribution on methanol selectivity and provides a reference for the future rational design and preparation of highly selective catalysts for CO₂ hydrogenation to methanol.