Realizing synergy between Cu, Ga, and Zr for selective CO2 hydrogenation to methanol

Abstract

Hydrogenating CO2 to methanol with high yields and selectivity remains a kinetic challenge. We report ternary Cu-Ga-Zr catalysts with promising performances. Methanol productivity and selectivity were highest on coprecipitated samples containing approximately 20wt% of each metal. At 7% isoconversion, this ternary system was more selective to methanol (60 ± 1%) than CuZrOx (51 ± 1%) and CuGaOx (53 ± 3%) at the same Cu loading. We uncover the importance of the Cu/Zr interface for CO2 adsorption, Cu/Ga interface for H adsorption, and metallic Cu for H–H dissociation. Methanol formation on these catalysts was found to be first order in H2, implying the reaction was likely to be rate-limited by hydrogen activation. In fact, the methanol space-time yield correlated linearly with the H2/D2 exchange rate. We propose a catalytic pathway wherein the production of the byproduct CO is hindered by the presence of adsorbed H.