Atomic Pd-promoted ZnZrO<inf>x</inf> solid solution catalyst for CO<inf>2</inf> hydrogenation to methanol

Abstract

The development of efficient CO2 conversion catalysts is a long-lasting desire. Herein, we introduce an atomic Pd-promoted ZnZrOx solid solution catalyst (Pd-ZnZrOx), which shows markedly enhanced rate of methanol production compared to bare ZnZrOx, as well as excellent stability over 100 h on stream. Up to 0.8 at% (i.e. 0.6 wt%), Pd can be atomically dispersed in ZnZrOx, leading to more oxygen vacancies on the mixed oxide that foster methanol production. Kinetic analysis and in situ DRIFTS reveal that hydrogen activation is limited on ZnZrOx, but Pd doping facilitates H2 dissociation as well as the consequent formation of HCOO*, thus boosting CO2 conversion to methanol. DFT analyses suggest that the presence of atomic Pd enables a more exothermic H2 dissociation, which increases the availability of surface H and facilitates CO2 hydrogenation on adjacent Zn sites, providing rationale on the high activity and robustness of Pd-ZnZrOx in CO2 hydrogenation.