6 research outputs found
The Oxidation State of Iron in Silicate Minerals from the Matrices of CO Carbonaceous Chondrites
No abstract available
The Oxidation State of Iron in Silicate Minerals from the Matrices of CO Carbonaceous Chondrites
No abstract available
Micro scale evolution of surface chemistry and morphology of the key components in operating hydrocarbon-fuelled SOFC
Replacement of hydrogen with hydrocarbon fuels in solid-oxide fuel cells (SOFCs) is an appealing alternative for
reducing the implementation costs of SOFCs technology, but the electrode stability and susceptibility to carbon deposition still
remain important issues to be solved. The present in situ photoelectron microscopy study of a prototype hydrocarbon-fuelled
SOFC, operated at 650 °C in C2H4 + H2O gas mixture and voltages in the range 0−3 V, provides insights into morphologychemistry
changes of the Ni electrodes and Cr interconnects with decisive impact on the electrochemical activity and durability.
The results reveal the combination of thermal and electromigration of Ni across the electrode−electrolyte interface that can
cause sensible material losses and structural changes responsible for the deterioration of device performance. The C 1s spectra
evidence deposition of C and formation of carbides on the Ni electrodes and Cr interconnects at 650 °C as result of C2H4
dissociation, the process being promoted applying cathodic potential and reversed by switching to anodic potential. Following
the attenuation of the C signal under anodic potential, the effect of the stability of different carbides on the reaction rate was
observed
In-situ photoelectron microspectroscopy during the operation of a single-chamber SOFC
This paper reports the first in-situ synchrotron-based scanning photoelectron microscopy study of an operating
YSZ-supported single-chamber SOFCwith Au–MnO2 composite cathode and NiO anode, fedwith 10−5 mbar 1:1
mixture of CH4 fuel and O2 at 650 °C.We employed a YSZ-supported cell with Au–MnO2 composite cathode and
NiO anode. The chemical imaging and micro-XPS results were complemented with simultaneous electrochemical
measurements, open circuit potential, potentiostatic and impedance spectrometry. The cell was operated
under two conditions: (i) with fully oxidized electrodes and (ii) after in-situ reductive activation of the anode.
The current delivered by the cell after in-situ reduction was about one order of magnitude higher. The chemical
states of Ni and Mn were affected by the in-situ reduction process but they were not modified by the fuel-cell
operation. Notwithstanding the absence of chemical state transformations of the electrode materials during
the prolonged fuel-cell operation, cell aging brings about morphological change, accompanied by a decrease of
the extracted current