Tailored design of novel Co⁰-Co^δ+ dual phase nanoparticles for selective CO₂ hydrogenation to ethanol

Catalytic hydrogenation of CO₂ to ethanol is a promising solution to address the greenhouse gas (GHG) emissions, but many current catalysts face efficiency and cost challenges. Cobalt based catalysts are frequently examined due to their abundance, cost-efficiency, and effectiveness in the reaction, where managing the Co⁰ to Co^δ+ ratio is essential. In this study, we adjusted support nature (Al₂O₃, MgO-MgAl₂O₄, and MgO) and reduction conditions to optimize this balance of Co⁰ to Co^δ+ sites on the catalyst surface, enhancing ethanol production. The selectivity of ethanol reached 17.9% in a continuous flow fixed bed micro-reactor over 20 mol% Co@MgO-MgAl₂O₄ (CoMgAl) catalyst at 270 °C and 3.0 MPa, when reduced at 400 °C for 8 h. Characterisation results coupled with activity analysis confirmed that mild reduction condition (400 °C, 10% H₂ balance N₂, 8 h) with intermediate metal support interaction favoured the generation of partially reduced Co sites (Co^δ+ and Co⁰ sites in single atom) over MgO-MgAl₂O₄ surface, which promoted ethanol synthesis by coupling of dissociative (CHx*)/non-dissociative (CHxO*) intermediates, as confirmed by density functional theory analysis. Additionally, the CoMgAl, affordably prepared through the coprecipitation method, offers a potential alternative for CO₂ hydrogenation to yield valuable chemicals.