Pressure-controlled selectivity in CO2 hydrogenation over Ag/In2O3 catalyst

Unraveling the mechanistic interplay between CO and CO2 hydrogenation over Ni, Co, and NiCo catalysts

Tuning CO2 hydrogenation selectivity via metal-oxide interfacial sites

Ordered mesoporous NiMg bimetal oxides confined KMoS catalyst for selective CO hydrogenation into higher alcohols

Selective hydrogenation of CO2 into dimethyl ether over hydrophobic and gallium-modified copper catalysts

Novel “CoCuNb” ternary catalysts with bimodal nanosized particle structure, in the absence of a generic support material, were designed and successfully tested in higher alcohol production via CO hydrogenation. The selectivities to primary alcohols with an optimized C2–C5 slate usually exceeded the 50 wt % level, and the combined selectivities to 1-alcohols/1-alkenes reached up to ∼73 wt % for CO conversions ranging between ∼5% and nearly 20%. The bimodal nanosized particle distribution, achieved through oxalate coprecipitation, contained Co–Cu particles with sizes ranging from 25 to 40 nm. Smaller particles between 4 and 8 nm were identified as Nb oxides and played the role of a structural dispersant (“spacer”) and promoter of 1-alcohol/1-olefin production. X-ray photoelectron spectroscopy revealed NbOx to contain major amounts of species with Nb in the 4+ oxidation state.

Improving methanol selectivity in CO2 hydrogenation by tuning the distance of Cu on catalyst

Boosting the selectivity of Pt catalysts for cinnamaldehyde hydrogenation to cinnamylalcohol by surface oxidation of SiC support

EDITORIAL

Selective hydrogenation of CO2 and CO into olefins over Sodium- and Zinc-Promoted iron carbide catalysts

Selective CO methanation on isostructural Ru nanocatalysts: The role of support effects

The CO2 electroreduction to fuels is a feasible approach to provide renewable energy sources. Therefore, it is necessary to conduct experimental and theoretical investigations on various catalyst design strategies, such as electronic metal-support interaction, to improve the catalytic selectivity. Here a solvent-free synthesis method is reported to prepare a copper (Cu)-based metal-organic framework (MOF) as the precursor. Upon electrochemical CO2 reduction in aqueous electrolyte, it undergoes in situ decomposition/redeposition processes to form abundant interfaces between Cu nanoparticles and amorphous carbon supports. This Cu/C catalyst favors the selective and stable production of CH4 with a Faradaic efficiency of ≈55% at -1.4V versus reversible hydrogen electrode (RHE) for 12.5h. The density functional theory calculation reveals the crucial role of interfacial sites between Cu and amorphous carbon support in stabilizing the key intermediates for CO2 reduction to CH4 . The adsorption of COOH* and CHO* at the Cu/C interface is up to 0.86eV stronger than that on Cu(111), thus promoting the formation of CH4 . Therefore, it is envisioned that the strategy of regulating electronic metal-support interaction can improve the selectivity and stability of catalyst toward a specific product upon electrochemical CO2 reduction.

The high catalytic performance of core–shell nanoparticles is usually attributed to their distinct geometric and electronic structures. Here we reveal a dynamic mechanism that overturns this conventional understanding by a direct environmental transmission electron microscopy visualization coupled with multiple state-of-the-art in situ techniques, which include synchrotron X-ray absorption spectroscopy, infrared spectroscopy and theoretical simulations. A Ni–Au catalytic system, which exhibits a highly selective CO production in CO2 hydrogenation, features an intact ultrathin Au shell over the Ni core before and after the reaction. However, the catalytic performance could not be attributed to the Au shell surface, but rather to the formation of a transient reconstructed alloy surface, promoted by CO adsorption during the reaction. The discovery of such a reversible transformation urges us to reconsider the reaction mechanism beyond the stationary model, and may have important implications not only for core–shell nanoparticles, but also for other well-defined nanocatalysts. The structure of core–shell catalysts is often assumed to be conserved over a reaction. Now, an in situ study reveals that the shell of Ni@Au nanoparticles is reversibly converted into a Ni–Au alloy during CO2 hydrogenation, with important mechanistic implications.

Many oxide catalysts exhibit high selectivity but low conversion in CO2 hydrogenation due to strong CO2 adsorption, which often impedes H2 dissociation and subsequent hydrogenation. Herein, we report that a ZnCr2O4@ZnOx catalyst featuring monodispersed ZnOx overlayer confined on ZnCr2O4 facilitates CO2 activation without compromising H2 activation. This catalyst demonstrates a dual-site mechanism in which ZnCr2O4 surface and/or ZnOx/ZnCr2O4 interface provide sites for CO2 activation and monodispersed ZnOx promote homolytic H2 dissociation and formation of stable metal─H species, enabling formate formation through hydrogen spillover to CO2 adsorption sites for hydrogenation at 303K. In contrast, H2 activation on ZnO or ZnCr2O4 suffers from the poisoning effect of strong CO2 adsorption. Consequently, the ZnCr2O4@ZnOx catalyst shows 2-8 folds enhancement in CO2 hydrogenation between 623-773K than ZnO and maintains 33% conversion and 100% CO selectivity at 723K over 150h. The established structure-performance relationship illustrates the critical role of dual-site catalysis and hydrogen spillover in hydrogenation reaction.

HI-Light: A Glass-Waveguide-Based "Shell-and-Tube" Photothermal Reactor Platform for Converting CO2 to Fuels.

Core–shell nanoparticles are being considered for various applications due to their controllable atomic structure and improved properties compared to their bulk counterparts. In the present work, we have synthesized Cu@Mn3O4 and Cu@Co3O4 (core@shell) nanocatalysts using wet-chemical synthesis methods involving organic surfactants, and probed their surfaces using CO and H2 under reaction conditions using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The surfactant ligands used in the synthesis of the nanoparticles must be removed to allow access to the active catalyst sites. These ligands can be removed by oxidation, allowing adsorption of CO and H2. This work reports the DRIFTS results of CO adsorption and hydrogenation on Cu@Mn3O4 and Cu@Co3O4 nanoparticles after removing the ligands. The CO hydrogenation results were in agreement with the DRIFTS results, which suggested that the Cu@Co3O4 nanoparticles adsorb CO both dissociatively and associatively, creating a balance between molecular CO required for CO insertion and dissociated surface carbon species required for chain growth. This resulted in higher selectivities towards C2+ alcohols on this catalyst. On the other hand, the Cu@Mn3O4 nanoparticles showed a higher CO uptake and a lower CO dissociation activity, which resulted in a lower CHx concentration on the surface, thus limiting the rate of the CO insertion step required to form higher alcohols.