Uncertainty Quantification of the Water-Gas Shift Reaction By Pt/CeO2 Catalyst

An uncertainty quantification framework¹ is applied to the water-gas shift reaction by Pt/CeO₂ catalyst. The PBE functional with Hubbard U parameters 5, 4 and 2 eV and the Heyd-Scuzeria-Ernzerhof (HSE) functional are combined in a factor analysis to obtain a prior gaussian uncertainty with correlations for intermediates and transition states. The overall thermodynamics are corrected using a uniform dirichlet distribution and the correction is spread among uncertainty in the gas molecules. A Bayesian inverse problem is conducted on an interface model² and a Pt(111) model using experiments from Ribeiro, et al³. The experiments used for the Bayesian inverse are turnover frequency, reaction orders and apparent activation barrier. The Bayesian inverse problem provides a posterior uncertainty on the energies of intermediates and transition states and an evidence value. The evidence value is used to make a model comparison between the interface model and the Pt(111) model to determine which model better explains experiments. On the interface model, multiple catalytic cycles are competitive for the highest turnover frequency. Finally, uncertainties in the degrees of rate control are presented providing insight on rate-controlling steps.

[1] Walker, E.; Terejanu, G. A.; Ammal, S. C.; Heyden, A. J. Phys. Chem. C. accepted-

http://pubs.acs.org/doi/abs/10.1021/acs.jpcc.6b01348 (2016).

[2] Aranifard, S.; Ammal, S. C.; Heyden, A. J. Catal. 309 (2014) 314-324.

[3] Phatak, A. A.; Koryabkina, N.; Rai, S.; Ratts, J. L.; Ruettinger, W.; Farrauto, R. J.; Blau, G. E.; Delgass, W. N.; Ribeiro, F. H. Catal. Today 123 (2007) 224-234.