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Title: Density functional theory studies of HCOOH decomposition on Pd(111)

Authors:
;
Publication Date:
Research Org.:
Energy Frontier Research Centers (EFRC) (United States). Institute for Atom-efficient Chemical Transformations (IACT)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1370182
DOE Contract Number:
AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Surface Science; Journal Volume: 650; Journal Issue: C; Related Information: IACT partners with Argonne National Laboratory (lead); Brookhaven National Laboratory; Northwestern University; Purdue University; University of Wisconsin at Madison
Country of Publication:
United States
Language:
English

Citation Formats

Scaranto, Jessica, and Mavrikakis, Manos. Density functional theory studies of HCOOH decomposition on Pd(111). United States: N. p., 2016. Web. doi:10.1016/j.susc.2015.11.020.
Scaranto, Jessica, & Mavrikakis, Manos. Density functional theory studies of HCOOH decomposition on Pd(111). United States. doi:10.1016/j.susc.2015.11.020.
Scaranto, Jessica, and Mavrikakis, Manos. 2016. "Density functional theory studies of HCOOH decomposition on Pd(111)". United States. doi:10.1016/j.susc.2015.11.020.
@article{osti_1370182,
title = {Density functional theory studies of HCOOH decomposition on Pd(111)},
author = {Scaranto, Jessica and Mavrikakis, Manos},
abstractNote = {},
doi = {10.1016/j.susc.2015.11.020},
journal = {Surface Science},
number = C,
volume = 650,
place = {United States},
year = 2016,
month = 8
}
  • Here, the investigation of formic acid (HCOOH) decomposition on transition metal surfaces is important to derive useful insights for vapor phase catalysis involving HCOOH and for the development of direct HCOOH fuel cells (DFAFC). Here we present the results obtained from periodic, self-consistent, density functional theory (DFT-GGA) calculations for the elementary steps involved in the gas-phase decomposition of HCOOH on Pd(111). Accordingly, we analyzed the minimum energy paths for HCOOH dehydrogenation to CO 2 + H 2 and dehydration to CO + H 2O through the carboxyl (COOH) and formate (HCOO) intermediates. Our results suggest that HCOO formation is easiermore » than COOH formation, but HCOO decomposition is more difficult than COOH decomposition, in particular in presence of co-adsorbed O and OH species. Therefore, both paths may contribute to HCOOH decomposition. CO formation goes mainly through COOH decomposition.« less
  • We have applied the relaxed and self-consistent extension of constricted variational density functional theory (RSCF-CV-DFT) for the calculation of the lowest charge transfer transitions in the molecular complex X-TCNE between X = benzene and TCNE = tetracyanoethylene. Use was made of functionals with a fixed fraction (α) of Hartree-Fock exchange ranging from α = 0 to α = 0.5 as well as functionals with a long range correction (LC) that introduces Hartree-Fock exchange for longer inter-electronic distances. A detailed comparison and analysis is given for each functional between the performance of RSCF-CV-DFT and adiabatic time-dependent density functional theory (TDDFT) withinmore » the Tamm-Dancoff approximation. It is shown that in this particular case, all functionals afford the same reasonable agreement with experiment for RSCF-CV-DFT whereas only the LC-functionals afford a fair agreement with experiment using TDDFT. We have in addition calculated the CT transition energy for X-TCNE with X = toluene, o-xylene, and naphthalene employing the same functionals as for X = benzene. It is shown that the calculated charge transfer excitation energies are in as good agreement with experiment as those obtained from highly optimized LC-functionals using adiabatic TDDFT. We finally discuss the relation between the optimization of length separation parameters and orbital relaxation in the RSCF-CV-DFT scheme.« less
  • Iron- and cobalt-exchanged ZSM-5 are active catalysts for the dissociation of nitrous oxide. In this study, density functional theory was used to assess a possible reaction pathway for the catalytic dissociation of N2O. The active center was taken to be mononuclear [FeO]+ or [CoO]+, and the surrounding portion of the zeolite was represented by a 24-atom cluster. The first step of N2O decomposition involves the formation of [FeO2]+ or [CoO2]+ and the release of N2. The metal-oxo species produced in this step then reacts with N2O again, to release N2 and O2. The apparent activation energies for N2O dissociation inmore » Fe-ZSM-5 and Co-ZSM-5 are 39.4 and 34.6 kcal/mol, respectively. The preexponential factor for the apparent first-order rate coefficient is estimated to be of the order 107 s-1 Pa-1. While the calculated activation energy for Fe-ZSM-5 is in good agreement with that measured experimentally, the value of the preexponential factor is an order of magnitude smaller than that observed . The calculated activation energy for Co-ZSM-5 is higher than that reported experimentally. However, consistent with experiment, the rate of N2O decomposition on Co-ZSM-5 is predicted to be significantly higher than that on Fe-ZSM-5.« less
  • Methanol decomposition on the stoichiometric CeO 2(110) surface has been investigated using density functional theory slab calculations. Three possible initial steps to decompose methanol by breaking one of three bonds (O-H, C-O and C-H) of methanol were examined. The relative order of thermodynamic stability for the three possible bond scission steps is: C-H > O-H > C-O. We further isolated transition state and determined activation energy for each bond-breaking mode using the nudged elastic method. The activation barrier for the most favorable dissociation mode, the O-H bond scission, is 0.3 eV on the (110) surface. An even lower activation barriermore » (< 0.1 eV) has been obtained on the CeO 2(111) surface for the same bond-breaking mode. We aslo calculated the pre-exponential factors based on the harmonic approximation and obtained the overall rate constants at 300 and 500 K for all three initial decomposition steps. In contrast to the order of thermodynamic stability, the calculated bond breaking barriers indicated a different bond breaking order kinetically: O-H > C-O > C-H. Our results are consistent with the previous experimental observation that methoxy is the dominant surface species after a stoichiometric CeO 2 surface was exposed to methanol. The experimentally observed methanol chemistry was determined by the kinetics of initial dissociation steps rather than the thermodynamic stability of product states. Surface coverage of methanol was found to affect the relative stability between molecular and dissociative adsorption modes. Dissociative adsorption modes are preferred thermodynamically for methanol coverage up to 0.5 ML but only molecular adsorption was stable at full monolayer coverage. This work was supported by a Laboratory Directed Research and Development (LDRD) project of the Pacific Northwest National Laboratory (PNNL). The computations were performed using the Molecular Science Computing Facility in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL), which is a U.S. Department of Energy national scientific user facility located at PNNL in Richland, Washington. Computing time was made under a Computational Grand Challenge “Computational Catalysis”. Part of the computing time was also granted by the National Energy Research Scientific Computing Center (NERSC).« less