CO2-to-methanol conversion over promoted Cu/ZnO/Al2O3 catalysts by Ga, Zr, and Co: A comprehensive DFT and experimental study

• Systematic comparison of Zr, Ga, and Co promoters in Cu/ZnO/Al 2 O 3 catalysts for CO 2 -to-methanol conversion. • Co-precipitation yields superior copper dispersion and methanol productivity compared to impregnation. • Zr- and Ga-promoted catalysts show higher CO 2 conversion and methanol selectivity than Co-promoted samples. • Co promotion shifts selectivity toward CO and CH 4 , reducing methanol yield. • Experimental results supported by DFT indicate that promoter type and synthesis method strongly govern catalyst structure and performance. Methanol synthesis via CO 2 hydrogenation over Cu/ZnO/Al 2 O 3 catalysts is limited by low activity, deactivation, and the reverse water–gas shift reaction. In this study, the influence of Zr, Ga, and Co promoters was evaluated using both co-precipitation and impregnation methods. The catalysts were characterized by XRD, N 2 O chemisorption, H 2 -TPR, TGA, H 2 /CO 2 -TPD, and FE-SEM, while density functional theory (DFT) calculations provided qualitative insights into promoter effects on methoxy stabilization. Co-precipitated catalysts, particularly those containing Zr and Ga, showed improved copper dispersion, smaller crystallite sizes, and enhanced H 2 /CO 2 adsorption. Under reaction conditions (235 °C, 50 bar, H 2 /CO 2 = 3:1), Zr- and Ga-promoted catalysts achieved CO 2 conversions of 42 % and 38 % with methanol selectivities of 98 % and 89 %, respectively. In contrast, Co-promoted catalysts exhibited higher CO and CH 4 selectivities, indicating reduced suitability for methanol synthesis. These findings demonstrate that promoter type and synthesis route strongly influence the structural and catalytic properties of Cu-based catalysts for CO 2 hydrogenation to methanol.