Rhenium‐Based Dual‐Function Materials for Integrated CO₂ Capture and Methanation

Abstract

International audienceIntegrated CO2 capture and utilization (ICCU) is a promising transition route for mitigating flue-gas emissions while producing useful energy-carrying chemicals. This study reveals the potential of rhenium as an alternative to nickel or ruthenium for catalyzing CO2 methanation. It is shown that the mixing of Re/γ-Al2O3 with CeO2 or a synthetic hydrotalcite-derived Mg–Al oxide (layered double oxide [LDO]) provides tunable low-Re-content dual-function materials (DFMs) with 100% CO2 conversion and 100% methane selectivity at 300°C under cyclic operation. The direct deposition of rhenium, in an atomically dispersed form, onto CeO2 or LDO increases the methane yield up to 128 µmol/g per 10 + 10 min cycle, suggesting a synergy between catalytic and adsorbing functions. In contrast, these two systems are poorly selective to methane in conventional gas-phase CO2–H2 reaction, showing the beneficial effect of sequential adsorption–hydrogenation operation on selectivity. In terms of stability, Re/CeO2 appears as the most efficient DFM, showing stable methane production over 50 cycles, moderate deactivation in the presence of water, and full recovery after return to dry conditions. An operando diffuse reflectance infrared spectroscopy (DRIFTS) investigation of this catalyst under both ICCU and conventional hydrogenation discloses the nature of molecular adsorbates (CO, formates) and their dependence on the reaction regime. In situ Raman spectroscopy shows that the oxidation state of the active ReOx species undergoes only minor modifications upon alternating CO2 and H2 steps, maintaining predominantly Re7+ moieties