Ceria-Supported Cobalt Catalyst for Low-Temperature Methanation at Low Partial Pressures of CO2

The direct catalytic conversion of atmospheric CO2 to valuable chemicals is a promising solution to avert negative consequences of rising CO2 concentration. However, heterogeneous catalysts efficient at low partial pressures of CO2 still need to be developed. Here, we explore Co/CeO2 as a catalyst for the methanation of diluted CO2 streams. This material displays an excellent performance at reaction temperatures as low as 175 °C and CO2 partial pressures as low as 0.4 mbar (the atmospheric CO2 concentration). To gain mechanistic understanding of this unusual activity, we employed in situ X-ray photoelectron spectroscopy and operando infrared spectroscopy. The higher surface concentration and reactivity of formates and carbonyls—key reaction intermediates—explain the superior activity of Co/CeO2 as compared to a conventional Co/SiO2 catalyst. This work emphasizes the catalytic role of the cobalt-ceria interface and will aid in developing more efficient CO2 hydrogenation catalysts

Operando Spectroscopy Unveils the Catalytic Role of Different Palladium Oxidation States in CO Oxidation on Pd/CeO2 Catalysts

Aiming at knowledge-driven design of novel metal–ceria catalysts for automotive exhaust abatement, current efforts mostly pertain to the synthesis and understanding of well-defined systems. In contrast, technical catalysts are often heterogeneous in their metal speciation. Here, we unveiled rich structural dynamics of a conventional impregnated Pd/CeO2 catalyst during CO oxidation. In situ X-ray photoelectron spectroscopy and operando X-ray absorption spectroscopy revealed the presence of metallic and oxidic Pd states during the reaction. Using transient operando infrared spectroscopy, we probed the nature and reactivity of the surface intermediates involved in CO oxidation. We found that while low-temperature activity is associated with sub-oxidized and interfacial Pd sites, the reaction at elevated temperatures involves metallic Pd. These results highlight the utility of the multi-technique operando approach for establishing structure–activity relationships of technical catalysts

Photocatalytic trifluoromethoxylation of arenes and heteroarenes in continuous-flow

The first example of photocatalytic trifluoromethoxylation of arenes and heteroarenes under continuous-flow conditions is described. Application of continuous-flow microreactor technology allowed to reduce the residence time up to 16 times in comparison to the batch procedure, while achieving similar or higher yields. In addition, the use of inorganic bases was demonstrated to increase the reaction yield under batch conditions

Supplementary data for the paper: Photocatalytic trifluoromethoxylation of arenes and heteroarenes in continuous-flow

The dataset contains characterization of compounds obtained via trifluoromethoxylation processes under photochemical conditions

Breaking structure sensitivity in CO2 hydrogenation by tuning metal–oxide interfaces in supported cobalt nanoparticles

A high dispersion of the active metal phase of transition metals on oxide supports is important when designing efficient heterogeneous catalysts. Besides nanoparticles, clusters and even single metal atoms can be attractive for a wide range of reactions. However, many industrially relevant catalytic transformations suffer from structure sensitivity, where reducing the size of the metal particles below a certain size substantially lowers catalytic performance. A case in point is the low activity of small cobalt nanoparticles in the hydrogenation of CO and CO2. Here we show how engineering of catalytic sites at the metal–oxide interface in cerium oxide–zirconium dioxide (ceria–zirconia)-supported cobalt can overcome this structure sensitivity. Few-atom cobalt clusters dispersed on 3 nm cobalt(II)-oxide particles stabilized by ceria–zirconia yielded a highly active CO2 methanation catalyst with a specific activity higher than that of larger particles under the same conditions

Breaking structure sensitivity in CO\u2082 hydrogenation by tuning metal-oxide interfaces in supported cobalt nanoparticles

A high dispersion of the active metal phase of transition metals on oxide supports is important when designing efficient heterogeneous catalysts. Besides nanoparticles, clusters and even single metal atoms can be attractive for a wide range of reactions. However, many industrially relevant catalytic transformations suffer from structure sensitivity, where reducing the size of the metal particles below a certain size substantially lowers catalytic performance. A case in point is the low activity of small cobalt nanoparticles in the hydrogenation of CO and CO2. Here we show how engineering of catalytic sites at the metal–oxide interface in cerium oxide–zirconium dioxide (ceria–zirconia)-supported cobalt can overcome this structure sensitivity. Few-atom cobalt clusters dispersed on 3 nm cobalt(II)-oxide particles stabilized by ceria–zirconia yielded a highly active CO2 methanation catalyst with a specific activity higher than that of larger particles under the same conditions