PdZn bimetallic nanoparticles for CO2 hydrogenation to methanol: Performance and mechanism

By means of density functional theory calculation, an exploration is conducted into the catalytic performance and reaction mechanism of CO2 hydrogenation to methanol on Pd32Zn6 (alloy), Pd32Zn6 (shell/core), and Pd38 nanoparticles. The potential preferred adsorption sites and adsorption energies of all the reaction species are determined. In particular, the electronic structure analysis of CO2 adsorption reveals the significant orbital hybridization occurring between the adsorbed CO2 molecule and Pd atoms, indicating that CO2 molecule is desirably activated and fully prepared for further hydrogenation. Furthermore, the reaction energies and activation barriers to the elementary reactions involved in the HCOO pathway are calculated precisely for the three nanoparticles. Compared with Pd38, the kinetically preferred pathway of methanol synthesis has shown changes after the introduction of Zn, and the activation barrier to the rate-determining step of the reaction route is also reduced on Pd32Zn6 (alloy) and Pd32Zn6 (shell/core) nanoparticles. It is suspected that the PdZn nanoparticle with an alloy structure exhibits higher activity of CO2 hydrogenation to methanol than that with a shell/core structure, which is attributed to the former having a lower activation barrier to the rate-determining step.