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On the Importance of the Associative Carboxyl Mechanism for the Water-Gas Shift Reaction at Pt/CeO2 Interface Sites.

Abstract: 

Periodic density functional theory calculations and microkinetic modeling are used to investigate the associative carboxyl pathways of the water-gas shift (WGS) reaction at the Pt/CeO2 (111) interface. Analysis of a microkinetic model based on parameters obtained from first principles suggests that the turnover
frequencies for the CO-assisted associative carboxyl mechanism are
comparable to experimental results. However, this microkinetic model containing various associative carboxyl pathways at interface sites cannot explain the experimentally observed activation barriers and reaction orders of Pt/CeO2 catalysts. Considering furthermore that a model of an associative carboxyl mechanism with redox regeneration, also derived from first principles and recently published by us, accurately predicts all kinetic parameters while displaying a 2 orders of magnitude higher turnover frequency, we conclude that at Pt/CeO2 interface sites, the WGS reaction follows a bifunctional Mars−van Krevelen mechanism in which support oxygen vacancies facilitate water dissociation.

Citation: 
Aranifard S, SC Ammal, and A Heyden.2014."On the Importance of the Associative Carboxyl Mechanism for the Water-Gas Shift Reaction at Pt/CeO2 Interface Sites."Journal of Physical Chemistry C 118(12):6314-6323. doi:10.1021/jp5000649
Authors: 
S Aranifard
SC Ammal
A Heyden