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‐Al2O3 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. Sustainable energy technology: Ni/UOx catalysts feature outstanding and durable methanation performance under exceptionally low‐temperature conditions or autothermal regime. A weakly radioactive nuclear by‐product (UOx) is engaged for the hot‐spots control in a highly exothermic process while converting extra‐heat into useful energy for promoting the chemoselective CO2‐to‐CH4 transformation.