The effect of K promotion and CoO crystal forms on the catalytic performance of CoO/CNTs catalysts for CO2 hydrogenation

Abstract In this work, carbon nanotubes (CNTs) were employed as supports, and CoO particles with hexagonal close-packed (hcp) or face-centered cubic (fcc) structures were deposited via ultrasonic impregnation. The influence of CoO crystal structure and potassium promotion on the catalytic performance of the supported catalysts was systematically investigated. Compared with hcp-CoO, fcc-CoO was more uniformly dispersed on CNTs, and potassium addition further stabilized cobalt dispersion. The CNTs supports effectively stabilized the CoO oxidation state, with a significant fraction of CoO retained after reaction at 400 °C. hcp-CoO/CNTs displayed markedly higher activity than fcc-CoO/CNTs, and product selectivity evolved very differently between the two catalysts. The synergy between potassium promotion and CoO phase control significantly enhanced CO and C 2+ hydrocarbon selectivity. Reduction of CoO to Co⁰ at elevated temperatures substantially increased CO₂ hydrogenation activity, albeit with a pronounced rise in CH 4 selectivity.