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Title: Combined Theoretical and Experimental Approach to the Discovery of Electrochemically Active Mixed Polyanionic Phosphatonitrates, AFePO 4 NO 3 (A = NH 4 /Li, K)

Authors:
;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
UNIVERSITYOTHER
OSTI Identifier:
1324793
Resource Type:
Journal Article
Resource Relation:
Journal Name: Chemistry of Materials; Journal Volume: 28; Journal Issue: 14
Country of Publication:
United States
Language:
ENGLISH

Citation Formats

Yaghoobnejad Asl, Hooman, and Choudhury, Amitava. Combined Theoretical and Experimental Approach to the Discovery of Electrochemically Active Mixed Polyanionic Phosphatonitrates, AFePO 4 NO 3 (A = NH 4 /Li, K). United States: N. p., 2016. Web. doi:10.1021/acs.chemmater.6b01755.
Yaghoobnejad Asl, Hooman, & Choudhury, Amitava. Combined Theoretical and Experimental Approach to the Discovery of Electrochemically Active Mixed Polyanionic Phosphatonitrates, AFePO 4 NO 3 (A = NH 4 /Li, K). United States. doi:10.1021/acs.chemmater.6b01755.
Yaghoobnejad Asl, Hooman, and Choudhury, Amitava. 2016. "Combined Theoretical and Experimental Approach to the Discovery of Electrochemically Active Mixed Polyanionic Phosphatonitrates, AFePO 4 NO 3 (A = NH 4 /Li, K)". United States. doi:10.1021/acs.chemmater.6b01755.
@article{osti_1324793,
title = {Combined Theoretical and Experimental Approach to the Discovery of Electrochemically Active Mixed Polyanionic Phosphatonitrates, AFePO 4 NO 3 (A = NH 4 /Li, K)},
author = {Yaghoobnejad Asl, Hooman and Choudhury, Amitava},
abstractNote = {},
doi = {10.1021/acs.chemmater.6b01755},
journal = {Chemistry of Materials},
number = 14,
volume = 28,
place = {United States},
year = 2016,
month = 7
}
  • Using a combination of in-situ and ex-situ X-ray Diffraction (XRD), photoelectron spectroscopy (XPS), catalyst reactivity performance studies and ab initio molecular dynamics (AIMD) simulations, the promoting role of lanthanum oxide (La2O3) in the catalytic synthesis of mixed higher (C2-C6) alcohols from syngas on Co based catalysts was investigated. XRD measurements show that doping with La (0.5 wt %) onto activated carbon (AC) supported Co catalyst enhances the Co2C phase formation while the Co2C phase formation is largely suppressed on alumina supported Co catalyst. A strong correlation of the selectivity towards alcohols with the ratio of Co2C/Co presented in the catalystsmore » was observed. Our theoretical ab initio molecular dynamics (AIMD) simulations suggest that, on AC supports under the reaction conditions, La exists as an oxide phase in the form of small clusters in the vicinity of Co particles. It was found that Co2C formation is energetically favorable especially for smaller Co particles where La may be influencing the Co particle size. Theoretical mechanistic studies indicate that oxygenated hydrocarbons can be formed on these catalysts by multiple routes involving. the formation of CHxO and CHxCO species at the interface between the La2O3 phase and Co/Co2C. A detailed comparison with previous findings in the literature, as well as discussion of the implications of these results upon the improvement if the selectivity of these catalysts towards higher alcohols, is presented. The Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.« less
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  • In this work we present a combined experimental and theoretical investigation of stable MgAl2O4 spinel-supported Rh and Ir catalysts for the steam methane reforming (SMR) reaction. Firstly, catalytic performance for a series of noble metal catalysts supported on MgAl2O4 spinel was evaluated for SMR at 600-850°C. Turnover rate at 850°C follows the order: Pd > Pt > Ir > Rh > Ru > Ni. However, Rh and Ir were found to have the best combination of activity and stability for methane steam reforming in the presence of simulated biomass-derived syngas. It was found that highly dispersed ~2 nm Rh andmore » ~1 nm Ir clusters were formed on the MgAl2O4 spinel support. Scanning Transition Electron Microscopy (STEM) images show that excellent dispersion was maintained even under challenging high temperature conditions (e.g. at 850°C in the presence of steam) while Ir and Rh catalysts supported on Al2O3 were observed to sinter at increased rates under the same conditions. These observations were further confirmed by ab initio molecular dynamics (AIMD) simulations which find that ~1 nm Rh and Ir particles (50-atom cluster) bind strongly to the MgAl2O4 surfaces via a redox process leading to a strong metal-support interaction, thus helping anchor the metal clusters and reduce the tendency to sinter. Density functional theory (DFT) calculations suggest that these supported smaller Rh and Ir particles have a lower work function than larger more bulk-like ones, which enables them to activate both water and methane more effectively than larger particles, yet have a minimal influence on the relative stability of coke precursors. In addition, theoretical mechanistic studies were used to probe the relationship between structure and reactivity. Consistent with the experimental observations, our theoretical modeling results also suggest that the small spinel-supported Ir particle catalyst is more active than the counterpart of Rh catalyst for SMR. This work was financially supported by the United States Department of Energy (DOE)’s Bioenergy Technologies Office (BETO) and performed at the Pacific Northwest National Laboratory (PNNL). PNNL is a multi-program national laboratory operated for DOE by Battelle Memorial Institute. Computing time was granted by a user proposal at the Molecular Science Computing Facility in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL) located at PNNL. Part of the computational time was provided by the National Energy Research Scientific Computing Center (NERSC).« less
  • No abstract prepared.
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