Engineering Lattice Dislocations of TiO2 Support of PdZn-ZnO Dual-Site Catalysts to Boost CO2 Hydrogenation to Methanol

Abstract

CO₂ hydrogenation to methanol using green hydrogen derived from renewable resources provides a promising method for sustainable carbon cycle but suffers from high selectivity towards byproduct CO. Here, we develop an efficient PdZn-ZnO/TiO₂ catalyst by engineering lattice dislocation structures of TiO₂ support. We discover that this modification orders irregularly arranged atoms in TiO₂ to stabilize crystal lattice, and consequently weakens electronic interactions with supported active phases. It facilitates the transformation of metallic Pd into PdZn alloy, effectively suppressing CO production through inhibiting the reverse water-gas shift reaction mediated by the carboxylate pathway on Pd⁰ sites. Moreover, it enables the efficient transfer of hydrogen species via hydrogen spillover from PdZn alloy to ZnO for compensating the poor hydrogen dissociation ability of ZnO, thereby creating both more oxygen vacancies essential for CO₂ activation and a hydroxyl-rich environment conducive to hydrogenation of intermediates. These collective modifications on PdZn-ZnO dual sites synergistically induce the propensity of the formate pathway for methanol synthesis. Consequently, compared to the unmodified catalyst, our as-designed catalyst increases methanol selectivity from 64.2 to 80.0 %, reduces CO selectivity from 35.0 to 19.8 %, and achieves an impressive methanol space-time yield of 9028.0 mg_MeOH g_Pd+Zn ^-1 h^-1 at a similar CO₂ conversion (~8.0 %).

Keywords: CO2 hydrogenation; Dual-site catalyst; Lattice dislocation; PdZn alloy; Reaction pathway.