1 research outputs found
Mechanistic Study of Pd–Cu Bimetallic Catalysts for Methanol Synthesis from CO<sub>2</sub> Hydrogenation
Density functional theory (DFT) calculations
were carried out to explore the adsorptions of reactive species and
the reaction mechanisms on Pd–Cu bimetallic catalysts during
CO<sub>2</sub> hydrogenation to methanol. All the possible preferred
adsorption sites, geometries, and adsorption energies of the relative
intermediates on pure Cu(111) and three PdCu(111) surfaces were determined,
revealing that both the adsorption configuration and corresponding
adsorption energy are changed by doping with Pd atoms. The strengthened
COOH* adsorption and the greatly weakened OH* adsorption change the
rate-limiting step from CO<sub>2</sub> hydrogenation forming <i>trans</i>-COOH* on Cu(111), Pd<sub>3</sub>Cu<sub>6</sub>(111),
and Pd<sub>6</sub>Cu<sub>3</sub>(111) surfaces to <i>cis</i>-COOH* decomposition forming CO* and OH* on Pd ML surface. Additionally,
the highest activation barriers for the overall reaction pathway are
reduced in the following trend: Cu(111) > Pd<sub>6</sub>Cu<sub>3</sub>(111) > Pd<sub>3</sub>Cu<sub>6</sub>(111) > Pd ML (monolayer).
Compared to the reaction on clean Cu(111) surface, the complete reaction
pathways for CH<sub>3</sub>OH synthesis on PdCu(111) surfaces, especially
on Pd ML, were facilitated and the yields of byproducts CO and CH<sub>4</sub> are suppressed, which corroborates well with experimental
reports showing that Pd–Cu bimetallic catalysts have a strong
synergistic effect on CO<sub>2</sub> hydrogenation to methanol. The
present insights are helpful for the design and optimization of highly
efficient Pd–Cu bimetallic catalysts used in CH<sub>3</sub>OH formation from CO<sub>2</sub> hydrogenation