Graphene-supported 2D cobalt oxides for catalytic applications.

2D materials are attracting increasing attention in many strategic applications. In particular, ultra-thin non-layered oxides have been shown to outperform their 3D counter-parts in several health and energy applications, such as the removal of toxic carbon monoxide by low temperature oxidation and the development of high performance supercapacitors. The general reason for that is the increased surface-to-volume ratio, which maximizes exposure of active species and enhances exchange between the (limited) bulk and the surface. The challenge is to synthesize such 2D configurations of 3D oxides, which generally requires quite harsh multi-step, multi-reagent chemical processes. Here we show that natural graphite can be used as a templating matrix to grow non-stoichiometric 2D transition metal oxides. We focus on highly porous, highly reduced cobalt oxides grown from cobalt nitrate and sodium borohydride under sonication. Extensive characterization, including nitrogen physisorption, thermogravimetric analysis (TGA), scanning and transmission electron microscopy (SEM/TEM), X-ray diffraction (XRD), temperature programmed oxidation and reduction (TPO/TPR), Fourier transformed infrared (FTIR) and Raman spectroscopies, highlights the specific features of the 2D morphologies (nanosheets and nanofilms) obtained. For comparison, 3D morphologies of Co3O4 spinel nanocrystallites are grown from stacked 2D cobalt phthalocyanine-graphene precursors upon controlled thermal oxidation. Finally, low temperature CO oxidation catalysis evidences the superior performance of the graphene-supported CoO-like cobalt oxide 2D nanosheets.

Not Just Another Methanation Catalyst: Depleted Uranium Meets Nickel for a High-Performing Process Under Autothermal Regime.

Ni-based catalysts prepared through impregnation of depleted uranium oxides (DU) have successfully been employed as highly efficient, selective, and durable systems for CO2 hydrogenation to substituted natural gas (SNG; CH4 ) under an autothermal regime. The thermo-physical properties of DU and the unique electronic structure of f-block metal-oxides combined with a nickel active phase, generated an ideal catalytic assembly for turning waste energy back into useful energy for catalysis. In particular, Ni/UOx stood out for the capacity of DU matrix to control the extra heat (hot-spots) generated at its surface by the highly exothermic methanation process. At odds with the benchmark Ni/γ-Al2 O3 catalyst, the double action played by DU as a "thermal mass" and "dopant" for the nickel active phase unveiled the unique performance of Ni/UOx composites as CO2 methanation catalysts. The ability of the weakly radioactive ceramic (UOx ) to harvest waste heat for more useful purposes was demonstrated in practice within a rare example of a highly effective and long-term methanation operated under autothermal regime (i. e., without any external heating source). This finding is an unprecedented example that allows a real step-forward in the intensification of "low-temperature" methanation with an effective reduction of energy wastes. At the same time, the proposed catalytic technology can be regarded as an original approach to recycle and bring to a second life a less-severe nuclear by-product (DU), providing a valuable alternative to its more costly long-term storage or controlled disposal.

Not Just Another Methanation Catalyst: Depleted Uranium Meets Nickel for a High-Performing Process Under Autothermal Regime.

Invited for this month's cover are collaborating teams from academia-the French ICPEES and IS2M of Centre national de la recherche scientifique (CNRS) and the Italian ICCOM of Consiglio Nazionale delle Ricerche (CNR)-and industry with the participation of the ORANO group. The cover picture shows a CO2 -to-CH4 process promoted by nickel nanoparticles supported on depleted uranium oxide under exceptionally low temperature values or autothermal conditions. The Research Article itself is available at 10.1002/cssc.202201859.