Effect of PdIn bimetallic particle formation on CO₂ reduction over the Pd-In/SiO₂ catalyst

A Pd-In/SiO₂ catalyst was prepared by the wet impregnation method and used for CO₂ reduction at atmospheric pressure. The catalyst was shown to have 100% selectivity toward CO with no detectable CH₄ formation. In order to understand the high CO selectivity of Pd-In/SiO₂, a detailed catalyst characterization in combination with the DFT study was conducted and compared with that over the Pd/SiO₂ catalyst. The XRD and TEM analyses indicate the formation of the PdIn bimetallic nanoparticles on Pd-In/SiO₂ after H₂ reduction. The unique catalytic property of Pd-In/SiO₂ was attributed to the formation of the bimetallic particles. Characterizations including H₂ chemisorption and DRIFT and DFT modeling show that the formation of PdIn bimetallic nanoparticles reduces the activity toward H₂ dissociative adsorption, weakens CO binding on the surface and increases the barrier of CO hydrogenation, suppressing the further hydrogenation beyond CO.