Experimental Studies of the Highly Active Cu–Ni/In₂O₃ Catalyst for CO₂ Hydrogenation to Methanol

The copper-based catalysts have been extensively exploited for the hydrogenation of CO2 to methanol. The In2O3-supported copper catalyst has also been investigated. However, its activity is not satisfactory, compared to that of other metal-promoted In2O3 catalysts. Herein, the In2O3-supported Cu–Ni bimetallic catalyst with a high dispersion of Ni and Cu species was prepared by chemical reduction. The addition of nickel leads to significantly higher activity at each temperature tested compared to Cu/In2O3. The activity of the bimetallic catalyst is also slightly higher than that of Ni/In2O3. For example, over Cu–Ni/In2O3 with a ca. 5/5 Cu/Ni weight percentage ratio, the CO2 conversion reaches 12.7% at 275 °C with a methanol selectivity of 66.6% and a methanol STY of 0.46 gMeOH gcat–1 h–1. However, the CO2 conversion and methanol selectivity are only 5.9 and 68.7% for Cu/In2O3 and 12.1 and 62.7% for Ni/In2O3 under the same condition. The use of Ni promotes the dispersion and activity of Cu/In2O3 and improves the stability of oxygen vacancies on the surface of In2O3, inhibiting the formation of the CuIn alloy. With the assistance of nickel, the Cu species also causes the formation of strongly CO adsorbed sites, resulting in improved methanol selectivity. Moreover, the Cu–Ni bimetallic catalyst has a strong hydrogen spillover effect, leading to more oxygen vacancies and improved CO2 adsorption.