Synergistical effect of CoIn alloy and oxygen vacancies over Co-In-Zr ternary catalysts boosting CO2 hydrogenation to methanol

Abstract

The hydrogenation of CO₂ to methanol using H₂ produced from renewable resources has been regarded as an effective way to mitigate CO₂ emissions. Unfortunately, how to obtain both high activity and methanol selectivity is still a trade-off challenge for catalyst development. Herein, we synthesize Co-In-Zr ternary metal oxide precursors via a simple hydrothermal method for hydrogenation of CO₂ to methanol. After reduction by H₂, a part of Co and In cations could be reduced from the solid solution to generate CoIn alloy, simultaneously constructing oxygen vacancy rich environment on the catalyst surface. The increased concentration of surface oxygen vacancies can improve the adsorption and activation of CO₂. Meanwhile, our findings show that the formed CoIn alloy significantly enhances the adsorption and dissociation of H₂, thus accelerating successive hydroconversion of CO₂ and intermediates to methanol. The synergy of CoIn alloy and oxygen vacancies significantly boosts both activity and methanol selectivity. Under the conditions of 300 °C and GHSV of 30,000 ml g_cat^-1 h^-1, the catalyst with a Co: In: Zr molar ratio of 1: 2: 7 achieves the CO₂ conversion of 10.2 %, the methanol selectivity of 81.5 %, and especially the methanol time-space yield up to 860 mg g_cat^-1 h^-1, surpassing the majority of the state-of-the-art In-based catalysts. Moreover, the catalyst exhibits the excellent stability, maintaining the performance within 100 h. Our work provides insights into designing efficient none-noble-metal catalysts for CO₂ hydrogenation reactions.