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

Integrated CO2 capture and utilization (ICCU) is a promising transition route for mitigating flue-gas emissions while producinguseful energy-carrying chemicals. This study reveals the potential of rhenium as an alternative to nickel or ruthenium forcatalyzing CO2 methanation. It is shown that the mixing of Re/γ-Al 2 O3 with CeO2 or a synthetic hydrotalcite-derived Mg–Aloxide (layered double oxide [LDO]) provides tunable low-Re-content dual-function materials (DFMs) with 100% CO 2 conversionand 100% methane selectivity at 300◦C under cyclic operation. The direct deposition of rhenium, in an atomically dispersedform, onto CeO2 or LDO increases the methane yield up to 128 µmol/g per 10 + 10 min cycle, suggesting a synergy betweencatalytic and adsorbing functions. In contrast, these two systems are poorly selective to methane in conventional gas-phase CO 2 –H 2 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 thepresence 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 activeReOx species undergoes only minor modifications upon alternating CO 2 and H2 steps, maintaining predominantly Re7+ moieties