Sustainable Ethanol Production via CO2 Hydrogenation with Enhanced Metal–Support Interfaces

Abstract

Cobalt-based catalysts were synthesized using the coprecipitation method from hydrotalcite precursors with CoO loadings of 10–50 mol %. Characterization was done using X-ray diffraction (XRD), N₂ physisorption, X-ray photoelectron spectroscopy (XPS), H₂-temperature-programmed reduction (TPR), and transmission electron microscopy (TEM), and their ethanol synthesis efficiency from CO₂ was tested in a fixed bed microreactor. The Co₃₀MgAl catalyst, with 30 mol % CoO, had highly dispersed Co nanoparticles and intermediate metal–support interaction, creating bifunctional Co^δ+ and Co⁰ sites for robust activity. It achieved peak ethanol selectivity of 22.4% at 300 °C, 4 MPa, and GHSV of 2 L g^–1 h^–1, with H₂/CO₂ = 3. Higher Co concentrations led to weaker metal–support interactions and methane production, while lower concentrations favored CO and methanol formation. The present study highlights the importance of intermediate metal–support interactions and optimal CoO loading (30 mol %) for improved CO₂-to-ethanol selectivity, supported by density functional theory (DFT) calculations.