Elucidating the Synergism by Applying Ni-Cu/Cr2O3 Catalysts for Green Methanol Fuel Synthesis by CO2 Hydrogenation

The CO2 hydrogenation process is thought to be one of the feasible methods for producing methanol fuel, which might be used to fulfill future energy demands. Improving the catalytic efficiency and understanding of the process are essential elements for the viability of CO2 conversion routes. Here, a co-precipitation method was used to synthesize Ni-Cu bimetallic catalysts supported by chromium oxide (Cr2O3). To examine nickel (Ni)’s promoting role, the synthesized catalysts were incorporated with different concentrations of Ni. The N2 adsorption–desorption isotherm exposed the mesoporous nature of Cr2O3-based Ni-Cu catalysts. A Fourier Transform Infrared (FTIR) spectroscopy investigation revealed the effective doping of Ni-Cu metal oxides on the surface of Cr2O3 by instigating an FTIR absorption band in the region associated with the FTIR absorption of metal oxides. The uniform morphology and homogenous, as well as highly dispersed, form of both Ni and Cu metal were recorded using a Field Emission Scanning Electron Microscope (FESEM) and X-ray Diffraction (XRD) techniques. The surface chemistry, metal–metal, and metal–support interactions of the Ni-Cu/Cr2O3 catalysts were disclosed via temperature program reduction (TPR) as well as X-ray photoelectron spectroscopy (XPS). The synergism between the Ni and Cu metals was revealed using both XPS and TPR techniques, which resulted in improving the catalytic profile of Ni-Cu/Cr2O3 catalysts. The activity data obtained by applying a slurry reactor demonstrated the active profile of Ni for CO2 reduction to methanol in terms of the methanol synthesis rate. The promoting role of Ni was established by observing the progressing and linear increase in methanol selectivity by Ni enrichment to the Ni-Cu/Cr2O3 catalysts. Structure and activity studies recognized the promoting role of Ni by experiencing metal–metal and metal–support interactions with highly dispersed metal oxides over the Cr2O3 support in the current case.