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Density Functional Theory Study on the Role of Polyacetylene as a Promoter in Selective Hydrogenation of Styrene on a Pd Catalyst
journal contribution
posted on 2017-02-13, 00:00 authored by Shunxin Fei, Bo Han, Qingfan Zhang, Ming Yang, Hansong ChengUnderstanding
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 Pd4 catalyst (Pd4/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 CC bond of the polymer substrate through the π–d
interaction, which further leads to charge rearrangement on the Pd4 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 Pd4 and Pd4/PA, the
mechanism that dictates the catalytic process on Pd4/PA
was identified. Charge analysis reveals that the enhanced catalytic
activity of Pd4/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 Pd4 catalytic system.
As a consequence, the absence of π orbitals of the PE substrate
may significantly reduce the electronic interaction between Pd4 and PE, which ultimately leads to the catalytic performance
similar to the activity on the pure Pd4 cluster.