Effective and Highly Selective CO Generation from CO₂ Using a Polycrystalline α‑Mo₂C Catalyst

Present experiments show that synthesized polycrystalline hexagonal α-Mo₂C is a highly efficient and selective catalyst for CO₂ uptake and conversion to CO through the reverse water gas shift reaction. The CO₂ conversion is ∼16% at 673 K, with selectivity toward CO > 99%. CO₂ and CO adsorption is monitored by DRIFTS, TPD, and microcalorimetry, and a series of DFT based calculations including the contribution of dispersion terms. The DFT calculations on most stable model surfaces allow for identifying numerous binding sites present on the catalyst surface, leading to a high complexity in measured and interpreted IR- and TPD-spectra. The computational results also explain ambient temperature CO₂ dissociation toward CO as resulting from the presence of surface facets such as Mo₂C­(201)-Mo/Cdisplaying Mo and C surface atomsand Mo-terminated Mo₂C­(001)-Mo. An <i>ab initio</i> thermodynamics consideration of reaction conditions, however, demonstrates that these facets bind CO₂ and CO + O intermediates too strongly for a subsequent removal, whereas the Mo₂C­(101)-Mo/C exhibits balanced binding properties, serving as a possible explanation of the observed reactivity. In summary, results show that polycrystalline α-Mo₂C is an economically viable, highly efficient, and selective catalyst for CO generation using CO₂ as a feedstock

Umweltgerechtes Verkehrsverhalten beginnt in den Köpfen

The control of the phase distribution in multicomponent nanomaterials is critical to optimize their catalytic performance. In this direction, while impressive advances have been achieved in the past decade in the synthesis of multicomponent nanoparticles and nanocomposites, element rearrangement during catalyst activation has been frequently overseen. Here, we present a facile galvanic replacement-based procedure to synthesize Co@Cu nanoparticles with narrow size and composition distributions. We further characterize their phase arrangement before and after catalytic activation. When oxidized at 350 °C in air to remove organics, Co@Cu core–shell nanostructures oxidize to polycrystalline CuO-Co₃O₄ nanoparticles with randomly distributed CuO and Co₃O₄ crystallites. During a posterior reduction treatment in H₂ atmosphere, Cu precipitates in a metallic core and Co migrates to the nanoparticle surface to form Cu@Co core–shell nanostructures. The catalytic behavior of such Cu@Co nanoparticles supported on mesoporous silica was further analyzed toward CO₂ hydrogenation in real working conditions