skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


  • NSF Public Access
  • Search Results
  • Exsolution of nanoparticles on A-site-deficient lanthanum ferrite perovskites: its effect on co-electrolysis of CO2 and H2O
Title: Exsolution of nanoparticles on A-site-deficient lanthanum ferrite perovskites: its effect on co-electrolysis of CO2 and H2O
La0.7Sr0.2Ni0.2Fe0.8O3 (LSNF), having thermochemical stability, superior ionic and electronic conductivity, and structural flexibility, was investigated as a cathode in SOECs. Exsolution of nanoparticles by reduction of LSNF at elevated temperatures can modulate the characteristics of adsorption, electron transfer, and oxidation states of catalytically active atoms, consequently improving the electrocatalytic activity. The exsolution of NiFe and La2NiO4 nanoparticles to the surface of LSNF under reducing atmosphere (5% H2/N2) was verified at various temperatures (500–800 °C) by IFFT from ETEM, TPR and in situ XRD. The exsolved nanoparticles obtained uniform size distribution (4.2–9.2 nm) and dispersion (1.31 to 0.61 × 104 particle per μm2) depending on the reduction temperature (700–800 °C) and time (0–10 h). The reoxidation of the reduced LSNF (Red-LSNF) was verified by the XRD patterns, indicative of its redox ability, which allows for redistribution of the nanoparticles between the surface and the bulk. TPD-DRIFTS analysis demonstrated that Red-LSNF had superior H2O and CO2 adsorption behavior as compared to unreduced LSNF, which we attributed to the abundance of oxygen vacancy sites and the exsolved NiFe and La2NiO4 nanoparticles. After the reduction of LSNF, the decreases in the oxidation states of the catalytically active ions, Fe and Ni, were characterized on the surface by XPS as well as in the bulk by XANES. The electrochemical performance of the Red-LSNF cell was superior to that of the LSNF cell for electrolysis of H2O, CO2, and H2O/CO2.  more » « less
Award ID(s):
1932638
PAR ID:
10354281
Author(s) / Creator(s):
; ; ; ; ; ;
Publisher / Repository:
RSC Publishing
Date Published:
Journal Name:
Journal of materials chemistry
ISSN:
2050-7488
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; (, Journal of Materials Chemistry A)
    La 0.7 Sr 0.2 Ni 0.2 Fe 0.8 O 3 (LSNF), having thermochemical stability, superior ionic and electronic conductivity, and structural flexibility, was investigated as a cathode in SOECs. Exsolution of nanoparticles by reduction of LSNF at elevated temperatures can modulate the characteristics of adsorption, electron transfer, and oxidation states of catalytically active atoms, consequently improving the electrocatalytic activity. The exsolution of NiFe and La 2 NiO 4 nanoparticles to the surface of LSNF under reducing atmosphere (5% H 2 /N 2 ) was verified at various temperatures (500–800 °C) by IFFT from ETEM, TPR and in situ XRD. The exsolved nanoparticles obtained uniform size distribution (4.2–9.2 nm) and dispersion (1.31 to 0.61 × 10 4 particle per μm 2 ) depending on the reduction temperature (700–800 °C) and time (0–10 h). The reoxidation of the reduced LSNF (Red-LSNF) was verified by the XRD patterns, indicative of its redox ability, which allows for redistribution of the nanoparticles between the surface and the bulk. TPD-DRIFTS analysis demonstrated that Red-LSNF had superior H 2 O and CO 2 adsorption behavior as compared to unreduced LSNF, which we attributed to the abundance of oxygen vacancy sites and the exsolved NiFe and La 2 NiO 4 nanoparticles. After the reduction of LSNF, the decreases in the oxidation states of the catalytically active ions, Fe and Ni, were characterized on the surface by XPS as well as in the bulk by XANES. The electrochemical performance of the Red-LSNF cell was superior to that of the LSNF cell for electrolysis of H 2 O, CO 2 , and H 2 O/CO 2 . 
    more » « less
  2. ; ; ; ; ; ; (, ChemCatChem)
    Abstract Oxidative coupling of methane (OCM) can be performed electrocatalytically by utilizing solid oxide cells, which provide a readily controlled oxygen supply through dense electrolytes. La0.7Sr0.2Ni0.2Fe0.8O3(LSNF) perovskite is an effective anode for OCM. Its surface characteristics and electrocatalytic activity can be improved by reduction and the resultant exsolution of bimetallic NiFe nanoparticles from its bulk. X‐ray diffraction (XRD) and environmental transmission electron microscopy proved that the evolution of hetero‐phases under reducing environment resulted in bimetallic NiFe nanoparticles being formed on the surface. A 36 % improvement in C2+hydrocarbon production rate was achieved due to the reduction of LSNF with the exsolved NiFe nanoparticles. Co‐feeding of H2O enhanced selective conversion of CH4resulting in the production rate of C2+hydrocarbons being increased by 56 %. Analysis of impedance spectra and in‐situ DRIFTS under a CH4+H2O atmosphere provided an understanding for the enhancement on the electrocatalytic OCM. 
    more » « less
  3. ; ; ; ; ; ; ; ; ; ; et al (, ACS Catalysis)
    A combination of several in situ techniques (XRD, XAS, AP-XPS, and E-TEM) was used to explore links between the structural and chemical properties of a Cu@TiOx catalyst under CO2 hydrogenation conditions. The active phase of the catalyst involved an inverse oxide/metal configuration, but the initial core@shell motif was disrupted during the pretreatment in H2. As a consequence of strong metal–support interactions, the titania shell cracked, and Cu particles migrated from the core to on top of the oxide with the simultaneous formation of a Cu–Ti–Ox phase. The generated Cu particles had a diameter of 20–40 nm and were decorated by small clusters of TiOx (<5 nm in size). Results of in situ XAS and XRD and images of E-TEM showed a very dynamic system, where the inverse oxide/metal configuration promoted the reactivity of the system toward CO2 and H2. At room temperature, CO2 oxidized the Cu nanoparticles (CO2,gas → COgas + Ooxide) inducing a redistribution of the TiOx clusters and big modifications in catalyst surface morphology. The generated oxide overlayer disappeared at elevated temperatures (>180 °C) upon exposure to H2, producing a transient surface that was very active for the reverse water–gas shift reaction (CO2 + H2 → CO + H2O) but was not stable at 200–350 °C. When oxidation and reduction occurred at the same time, under a mixture of CO2 and H2, the surface structure evolved toward a dynamic equilibrium that strongly depended on the temperature. Neither CO2 nor H2 can be considered as passive reactants. In the Cu@TiOx system, morphological changes were linked to variations in the composition of metal-oxide interfaces which were reversible with temperature or chemical environment and affected the catalytic activity of the system. The present study illustrates the dynamic nature of phenomena associated with the trapping and conversion of CO2. 
    more » « less
  4. (, Fuel)
    A simple procedure was developed to synthesize molybdenum carbide nanoparticles (Mo2C/BC) by carburization of molybdate salts supported on the biochar from pyrolysis of biomass without using extra carbon source or reducing gas. The molybdenum carbide formation procedure investigated by in-situ XRD and TGA-MS indicated that the phase transitions followed the path of (NH4)6Mo7O24·4H2O → (NH4)2Mo3O10 → (NH4)2Mo14O42 → Mo8O23 → Mo4O11 → MoO2 → Mo2C. The volatile gases CO, H2, and CH4 evolved from biochar and the biochar solid carbon participated in the reduction of molybdenum species, while the biochar and CH4 served as carbon sources for the carburization. Temperature programmed surface reactions of Mo2C/BC indicated that CH4 dissociated as CH4 ⇋ C∗ + 2H2 on the catalyst surface, and CO2 reacted as CO2 + C∗ ⇋ 2CO+ ∗ due to oxidation of Mo2C. Both experiment data and thermodynamic analysis for the study of operation conditions of CO2 reforming of CH4 clearly demonstrated that the yields of H2 and CO increased with the increased temperature and the reasonable conversions should be performed at 850 °C, at which both CH4 and CO2 conversions were higher than 80%. 
    more » « less
  5. ; ; ; (, Fuel Cells)
    Abstract High surface area graphitic mesoporous carbons (M‐mGMC; M=Ni, Fe, Co or Ni‐Fe) were synthesizedviacatalytic graphitization using a hard template based synthesis method. In house prepared SBA‐15 silica material was impregnated with metal precursors to obtain M/SBA‐15, template for M‐mGMC synthesis. These materials were studied using different material characterization techniques, such as nitrogen adsorption desorption (BET), X‐ray diffraction (XRD) analysis, Raman spectroscopy, X‐ray photoelectron spectroscopy (XPS), Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Specific surface area ranging from 1,227.9 m2g−1to 1,320.7 m2g−1was observed for four M‐mGMCs. Raman spectroscopy, XPS and wide angle XRD suggested presence of graphitic structure in these materials along with disorders. Electrocatalytic performance of these materials along with conventional carbon black (Vulcan XC‐72) were evaluated in a single‐stack proton exchange membrane fuel cell (PEMFC). Pt/NiFe‐mGMC exhibited enhanced electrocatalytic activity compared to Pt/Ni‐mGMC, Pt/Fe‐mGMC and Pt/Co‐mGMC electrocatalysts. However, Pt/NiFe‐mGMC lacked adequate proton transport in membrane electrode assembly (MEA) compared to Pt/Vulcan XC‐72. This exploratory study showed that NiFe‐mGMC may find application as electrocatalyst support material in PEMFC. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email