Electrochemical performance of Ni-based anodes for solid oxide fuel cells

The catalytic activity of Ni-based anodic materials was investigated in complete solid oxide fuel cells (SOFCs) by electrochemical analysis. Button cells, consisting of supporting yttria-stabilized zirconia (YSZ) electrolyte layer, (La1-xSrx)y MnO3 (LSM) cathode and (cermet) Ni0.5Co0.5\u2013YSZ anode were employed. Powders for anodes were obtained by wet impregnation. This pro- cedure allowed easy production of composite electrodes with homogeneous distribution of phases and controlled microstructure. Two electrodes impedance spectroscopy was carried out at different temperatures and partial pres- sures of reacting gases in order to evaluate contribution of each component to overall cell losses. Current\u2013voltage characteristic curves were also collected. Feeding with CH4 was tested and compared to H2. No deterioration of cell performance due to carbon formation at anode was observed over a test period of 100 h

Morphological control of hydrothermal Ni(OH)2 in the presence of polymers and surfactants: nanocrystals, mesocrystals, and superstructures

International audiencePolymers with different hydrophilic groups [polyvinylpyrrolidone (PVP), ammonium polyacrylate (APA), and hydroxypropylmethyl cellulose (HPMC)] and surfactants [cetyltrimethylammonium bromide (CTAB) and sodium dodecylbenzensulfonate (SDBS)] were used as additives to modify the crystallization of β-Ni(OH)2 in hydrothermal conditions. Marked morphological changes in the β-Ni(OH)2 particles were observed depending on the additive concentration and on the duration of the hydrothermal treatment. The final morphology is the result of a complex, time-dependent self-assembly and growth process. Well-defined particles with sizes from submicrometer range to a few micrometers corresponding to hexagonal lamellae, hexagonal tabular mesocrystals, rosette- and flowerlike aggregates of lamellae, hexagonal prismatic mesocrystals, and acicular nanocrystals were easily obtained after a short time (2−24 h) aging at 150−200 °C. With PVP and CTAB, there is evidence of a growth process dominated by self-assembly of nanocrystals to produce mesocrystals. The formation of spherical superstructures (with SDBS, up to 70 μm in diameter) and hollow spheres (with PVP) is observed at long times (>24 h) as a result of solvent-mediated recrystallization processes, like Ostwald ripening. The overall results show that hydrothermal synthesis of β-Ni(OH)2 in the presence of polymers with hydrophilic groups and surfactants is a versatile tool for crystal morphogenesis