The Catalyst Review July 2024 - 13

Experimental Abstracts
In Situ Exsolved CoFe Alloy Nanoparticles on Gd2SrCo0.8Fe1.2O7−Δ for Direct
Hydrocarbon Fuel Solid Oxide Fuel Cells
Solid oxide fuel cells (SOFCs) can transform the chemical energy within fuels into electrical energy without requiring combustion,
making them viable candidates for distributed power stations and portable power sources. This is due, in large part, to their all-solid
construction, large fuel selection (hydrogen or hydrocarbon fuels), wide working temperature range (400-1000°C), and excellent energy
conversion efficiency (45-65%). Efforts to develop novel anode materials to further
enhance their electrochemical properties have shown that Perovskite-type oxides show
significant promise due to their excellent mixed ionic/electronic conductivity, prominent
coking resistance, and high redox stability. Herein, the authors describe anodes
based on nanoparticle-impregnated Ruddlesden−Popper (RP)-type layered oxide
Gd2SrCo0.8Fe1.2O7− Δ (RP-GSCF), which demonstrate good catalytic activity in H2 and CH4
and excellent coking resistance in a CH4 fuel atmosphere.
A Ni-free solid oxide fuel cell (SOFC) ceramic anode composed of CoFe alloy (CFA)
nanoparticles evenly dispersed in porous Ruddlesden−Popper-type layered oxide
Gd2SrCo0.8Fe1.2O7− Δ (RP-GSCF) fabricated by an in situ reduction method. The crystal
structure of RP-GSCF powders before and after reduction in H2 at 800°C was studied
by XRD and exhibited a typical RP-type layered perovskite structure. SEM/TEM analysis
(Figure 1) showed that the microstructure of as-prepared porous RP-GSCF anodes
comprises well-interconnected particles with an average diameter of ~300 nm, ensuring
sufficient connection strength and facilitating gas diffusion of the anode. The raw RP-GSCF
powders were smooth, and no exsolved particle was found on their surface (Figure 1B).
In contrast, after being exposed in H2 at 800°C for 2h, some nanoparticles were exsolved
and uniformly dispersed on the surface of porous RP-GSCF backbones (Figure 1C). The
slight decrease of lattice oxygen and increase of adsorbed oxygen on the surface of
RP-GSCF-CFA are attributed to the exsolution of Co and Fe atoms from RP-GSCF along
Figure 1. SEM images of the as-prepared RPGSCF
(A, B) and RP-GSCF-CFA (C, D). TEM (E),
high-resolution TEM (HRTEM) image (F, G), and
SEAD pattern (H) of RP-GSCF-CFA.
with the formation of oxygen vacancies. The increase in surface oxygen vacancies in RPGSCF-CFA
may induce the promotion of its electrochemical activity. The DFT-calculated
results demonstrate that the higher concentration of vacant sites on the oxygen
sublattice, namely, the increase of oxygen vacancies,
would indirectly promote the oxide ion diffusion on the
surface of perovskite oxides.
Figure 2A shows the impedance spectra of lanthanum
strontium gallium magnesium oxide (LSGM) electrolytesupported
SOFC single cells under open-circuit voltage
(OCV) conditions at different temperatures in wet H2 (3 vol
% H2O) with RP-GSCF-CFA as the anode and lanthanum
Strontium Cobalt Ferrite (LSCF) as the cathode. The RPGSCF-CFA
anode demonstrated good catalytic activity
and coking resistance toward H2 and hydrocarbon fuels.
The LSGM electrolyte-supported single cell with the RPGSCF-CFA
anode and LSCF cathode can deliver peak
power densities of about 0.45 and 0.34 mW cm2 with
humidified H2 and CH4 (3 vol % H2O) at 800°C, respectively.
Moreover, the RP-GSCF-CFA anode demonstrates good
stability in wet CH4 for over 72 h. Li K, Tan T, Yang, C, et al.,
(2024). Energy Fuels, 38, 6403−6409
Figure 2. Electrochemical performance of RP-GSCF-CFA|LSGM|LSCF single cells, impedance
spectra under open-circuit voltage (OCV) in wet H2 (3 vol % H2O) (A). Total resistance (Rt),
interfacial polarization resistance (Rp), and ohmic resistance (Ro) determined from the
impedance spectra (B). Single-cell voltage and power density as a function of current density
in wet H2 (3 vol % H2O) (C) and wet CH4 (3 vol % H2O) (D) fuels at 700, 750, and 800°C.
The Catalyst Review
July 2024
13
The Catalyst Review July 2024

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