Highly Stable CO₂ Methanation Catalyst Fabricated by Engineering Metal-Metal Oxide Interfaces of CoAlO_x

Preparation of a heterogeneous catalyst with ultra-high catalytic stability and target product selectivity of > 99% at near thermodynamic equilibrium conversion is the ultimate goal to pursue in the catalysis field. Here, a CoAlO_x catalyst is constructed for CO₂ methanation by precisely engineering metal-metal oxide interfaces. It shows CO₂ conversion of > 87% and CH₄ selectivity of > 99% within 3000 h at 350°C, 1 MPa and GHSV of 12 000 mL g^-1 h^-1. Further prolonging of reaction time to 5000 h just slightly decreases CO₂ conversion to 77.5% without seriously affecting CH₄ selectivity. The CH₄ productivity approaches to 2463.6 mmol g^-1 h^-1 at GHSV of 375 000 mL g^-1 h^-1, being superior to reported noble metal- and transition metal-based catalysts. Such a catalytic performance stems from formation of Co⁰-CoO-Al₂O₃ microstructures with metallic Co⁰ nanoparticles stably trapped in atomically intimate CoO-Al₂O₃ material. The CoO-Al₂O₃ interfaces enhance CO₂ adsorption and transformation into carbonates and/or bicarbonates, whereas metallic Co⁰ promote H₂ dissociation and CO₂ hydrogenation. Technical and economic analyses show that CO₂ methanation could be profitable in places with abundant wind, photovoltaic, and other off-grid powers, or when the green hydrogen price is < 1103.40 US$/t, which could help build sustainable energy system in the future.