(758d) Design of Highly Active Cobalt Catalysts for CO2 Hydrogenation Via the Tailoring of Surface Orientation of Nanostructures

One promising route to mitigating CO₂ is through the use of point source technologies that upgrade CO₂ into high value products via the CO₂ hydrogenation mechanism. Due to the high thermodynamic stability of CO₂, catalytic routes are often required to convert CO₂ into high value products, particularly electrocatalytic and thermo-catalytic processes. The thermo-catalytic approach is often favored due the robust nature of the process, which can be readily scaled to demand and easily integrated into existing point source CO₂ sites such as power plants and industrial facilities outfitted with CO₂ capture. However, while several advances have been made in the mechanistic understanding of CO₂ hydrogenation, there is still need for an applied understanding that can be utilized to create catalyst that selectively favor the preferred product that couples spectroscopic evidence of the reaction intermediates of both the major reaction, and isolated subsequent reaction steps.

In this study, we illustrate how tailoring surface orientations of Co₃O₄ catalysts on the nanoscale results in control over catalytic performance via the preferential formation of active surface species during CO₂ hydrogenation. This resulted in over an order of magnitude increase in the methane turnover frequency on Co₃O₄ nanorods with the exposed {110}/{001} family of surface facets, as opposed to conventional Co₃O₄ nanoparticles with the exposed {111}/{001} family of surface facets. We found via in situ DRIFTS studies that this difference in catalytic performance for the Co₃O₄ nanorods was due to the inhibition of the formate spectator species. Furthermore, by studying the second hydrogenation step in CO₂ hydrogenation, which is CO hydrogenation, we were able to discern that the formation of bridged CO was the key difference between the two catalyst. Ultimately, this careful design approach provides a new dimension for the development of next generation catalysts and opens new, more efficient strategies for the conversion of carbon dioxide into useful hydrocarbons.