Carbon dioxide (CO2) hydrogenation has continued to receive significant attention as an effective route to recycle CO2 into usable products, such as methane, CO and methanol. CO2 hydrogenation to methane has the lowest Gibbs free energy below 500 oC and is the most feasible pathway among the three products from a thermodynamic perspective. However, methanol is a more valuable platform chemical and can also serve as a hydrogen storage medium. Yet, the identification of new catalyst compositions that avoid methane formation while maximizing methanol yields during CO2 hydrogenation remains a significant challenge. Ruthenium is one of the most active and selective catalysts for CO2 methanation. Efforts to modulate the selectivity of Ru-based catalysts for methanol synthesis have been made through the development of homogeneous, molecular catalysts; however, these catalysts often suffer from limited thermal stabilities and difficulties separating from the product to reuse/recycle. An alternative approach is through the formation of a bimetallic alloy, which alters the catalyst performance through electronic and geometric effects. Such an approach has been successful with In-Pd alloys that prohibits the CO methanation pathway. In this study, we evaluated In-Ru alloys for liquid phase CO2 hydrogenation. Our work showcases that incorporation of indium promotes methanol selectivity to over 90%, and it prohibits methane production at 200 oC where pure Ru produced 97% methane and Ga-Ru alloy produced mainly CO. In addition, we performed diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) experiments, CO TPR, H2-D2 exchange as well as formic acid hydrogenation studies. These experiments provide further insight into the role of In in tuning the interaction between surface species (formate, CO and hydrogen) and surface sites, leading to better methanol selectivity than pure Ru and Ga-Ru alloy.

Bimetallic Ru-based alloy nanoparticles: Unraveling the effects of In and Ga addition on methanol synthesis from CO2

ACS Spring Meeting 2021

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