Highly dispersed metal doping to ZnZr oxide catalyst for CO2 hydrogenation to methanol: Insight into hydrogen spillover

Abstract

Metallic oxide based catalysts have received much attention in CO2 hydrogenation to methanol because of their high methanol selectivity and long-term stability. But the relatively weak hydrogenation ability leads to low methanol activity. Here, we introduce a small amount of Cu (molar fraction < 2%) into ZnZrOx to form ternary metal oxide solid solution catalysts (x% CuZnZr) to promote methanol production. The optimized 0.5% CuZnZr catalyst performs CO2 conversion of 9.5% and methanol yield of 7.2%, both of which are about 4 times that of ZnZr catalyst at comparable methanol selectivity (76% versus 80%) at 290 °C. Chemisorption and in situ diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) analyses reveal that the enhanced activity is attributed to the improved hydrogenation capacity and accelerated transformation of HCOO* to CH3O* caused by hydrogen spillover from well dispersed Cu. This can also be applied to trace amount of Pd or Pt doping to ZnZrOx.