1 research outputs found
Density Functional Theory Study on the Role of Polyacetylene as a Promoter in Selective Hydrogenation of Styrene on a Pd Catalyst
Understanding
mechanisms of catalyst–substrate interactions
is of essential importance for the design and development of novel
catalysts with superior performances. In the present density functional
theory study, selective hydrogenation of styrene on a polyacetylene
(PA)-supported Pd<sub>4</sub> catalyst (Pd<sub>4</sub>/PA) was employed
as a model system to address how catalyst–substrate interactions
affect the charge state of Pd, which subsequently influences catalytic
activity. It was found that the Pd cluster can be anchored strongly
on the CC bond of the polymer substrate through the π–d
interaction, which further leads to charge rearrangement on the Pd<sub>4</sub> cluster with the top two Pd atoms being more negatively charged.
By comparing the calculated minimum energy profiles of styrene hydrogenation
on surfaces of both pure Pd<sub>4</sub> and Pd<sub>4</sub>/PA, the
mechanism that dictates the catalytic process on Pd<sub>4</sub>/PA
was identified. Charge analysis reveals that the enhanced catalytic
activity of Pd<sub>4</sub>/PA is largely attributed to the negative
charges on the two topmost Pd atoms, which facilitates both hydrogenation
of styrene and desorption of the product. Nevertheless, PA hydrogenation
to produce polyethylene (PE) was also found to be a potentially viable
process with a moderate activation barrier of 0.43 eV, which may consequently
lead to the formation of a PE-supported Pd<sub>4</sub> catalytic system.
As a consequence, the absence of π orbitals of the PE substrate
may significantly reduce the electronic interaction between Pd<sub>4</sub> and PE, which ultimately leads to the catalytic performance
similar to the activity on the pure Pd<sub>4</sub> cluster