Characterization of Y3+ Doped-Ba(Ce,Zr)O3 incorporated with NiO as composite anode for proton conducting fuel cell application / Shazana Mohd Senari

The high polarization resistance which contribute by electrode at intermediate
temperature operation (500-800°C) is one of the major challenges in the development
of proton conducting fuel cells (PCFCs). In this study, the focus was specified on
anode part where the oxidation process takes place. The work was divided into three
parts where the first part was given on the selection of NiO-Ba(Ce0.6Zr0.4)0.9Y0.1O3-δ
(NiO-BCZY) ratio (40:60, 50:50 and 60:40) and the best composition is proceed to the
synthesis of NiO-BCZY composite anode powder by three different synthesizing
methods; evaporation and decomposition of solution and suspension method (EDSS),
one-step sol-gel method and two-step sol-gel method. Then, the second part was
directed towards the characterization of the selected NiO-BCZY composite anode in
form of pellet. To prove the capability of the NiO-BCZY composite anode in PCFC
application, an anode supported single button cell with configuration of NiOBCZY|
BCZY|LSCF (LSCF: La0.6Sr0.4Co0.2Fe0.8O3-δ) was fabricated as a function of
BCZY electrolyte layer in part three. The synthesized NiO-BCZY composite anode
powders were characterized by Fourier Transform Infrared (FTIR) Spectroscopy, Xray
Diffractometer (XRD) and Field Emission Scanning Electron Microscopy/Energy
Dispersive X-ray (FESEM/EDX). The structural and microstructural study of
composite anode pellet was examined by XRD and FESEM analysis. The
electrochemical performance of the composite anode pellet and single button cell with
3 layers (SC_3L) and 10 layers (SC_10L) of electrolyte were evaluated using
Electrochemical Impedance Spectroscopy (EIS). The power density of the single
button cell was measured by in-house developed SOFC test station. As corroborated
by the FTIR, XRD and FESEM/EDX analyses, the one-step sol-gel method produced
excellent phase stability and better characteristic in term of microstructural and
morphological properties as compared to the two-step sol-gel method and EDSS
method. For the characterization of composite anode pellet, XRD analysis confirmed
the formation of Ni-BCZY composite anode and the FESEM images showed the
porous anode pellet after undergo the reduction process under wet H2:N2 (10%:90%).
Moreover, the increasing of conductivity in wet H2:N2 (10%:90%) verified that the
NiO in the composite anode was reduced to Ni metal. The evaluation of
electrochemical performance of the Ni-BCZY composite anode in an anode supported
single button cell revealed that the obtained polarization resistance is comparable with
other single button cell in literatures. The polarization resistances as well as the ohmic
resistances of the single button cells decreased as the operating temperature increased.
This observation shows that the involved reaction is thermally activated process.
However, the SC_3L exhibited better performance with polarization resistances
(Rp=0.52 Ωcm2) compared to SC_10L (Rp=6.31 Ωcm2). The performance of SC_3L
was further tested using fuel cell test station and shown a good power density of 332
mW cm-2. In conclusion, the NiO-BCZY synthesized by one-step sol-gel method has
the ability to produce a composite anode powder with good structural and
microstructural characteristics. The application of NiO-BCZY in single button cell has
surprisingly results in the significant improvement for single button cell performance.