Stabilization of catalyst particles against sintering on oxide supports with high oxygen ion lability exemplified by Ir-catalyzed decomposition of N2O

Iridium nanoparticles deposited on a variety of surfaces exhibited thermal sintering characteristics that were very strongly correlated with the lability of lattice oxygen in the supporting oxide materials. Specifically, the higher the lability of oxygen ions in the support, the greater the resistance of the nanoparticles to sintering in an oxidative environment. Thus with γ-Al2O3 as the support, rapid and extensive sintering occurred. In striking contrast, when supported on gadolinia-ceria and alumina-ceria-zirconia composite, the Ir nanoparticles underwent negligible sintering. In keeping with this trend, the behavior found with yttria-stabilized zirconia was an intermediate between the two extremes. This resistance, or lack of resistance, to sintering is considered in terms of oxygen spillover from support to nanoparticles and discussed with respect to the alternative mechanisms of Ostwald ripening versus nanoparticle diffusion. Activity towards the decomposition of N2O, a reaction that displays pronounced sensitivity to catalyst particle size (large particles more active than small particles), was used to confirm that catalytic behavior was consistent with the independently measured sintering characteristics. It was found that the nanoparticle active phase was Ir oxide, which is metallic, possibly present as a capping layer. Moreover, observed turnover frequencies indicated that catalyst-support interactions were important in the cases of the sinter-resistant systems, an effect that may itself be linked to the phenomena that gave rise to materials with a strong resistance to nanoparticle sintering

Effect of CuO as Sintering Additive in Scandium Cerium and Gadolinium-Doped Zirconia-Based Solid Oxide Electrolysis Cell for Steam Electrolysis

The effect of CuO as a sintering additive on the electrolyte of solid oxide electrolysis cells (SOECs) was investigated. 0.5 wt% CuO was added into Sc0.1Ce0.05Gd0.05Zr0.89O2 (SCGZ) electrolyte as a sintering additive. An electrolyte-supported cell (Pt/SCGZ/Pt) was fabricated. Phase formation, relative density, and electrical conductivity were investigated. The cells were sintered at 1373 K to 1673 K for 4 h. The CuO significantly affected the sinterability of SCGZ. The SCGZ with 0.5 wt% CuO achieved 95% relative density at 1573 K while the SCGZ without CuO could not be densified even at 1673 K. Phase transformation and impurity after CuO addition were not detected from XRD patterns. Electrochemical performance was evaluated at the operating temperature from 873 K to 1173 K under steam to hydrogen ratio at 70:30. Adding 0.5 wt% CuO insignificantly affected the electrochemical performance of the cell. Activation energy of conduction (Ea) was 72.34 kJ mol−1 and 74.93 kJ mol−1 for SCGZ and SCGZ with CuO, respectively

Fabrication of alloy foam-supported solid oxide electrolysis cell (SOEC) for hydrogen production

Alloy foam-supported SOEC is fabricated. Nickel-iron (Ni-Fe) alloy foam (Porosity: 5-130 ppi) is used for cell support. Single thin-cell composed of Ni- Sc0.1Ce0.05Gd0.05Zr0.89O2 (SCGZ) cathode, SCGZ electrolyte and Ba0.5Sr0.5Co0.8Fe0.2O3- δ (BSCF) anode is fabricated. Electrode powders are mixed with additives forming as slurry for wet chemical coating. 70%weight content of cermet provides smooth surface and sufficient viscosity to prevent slurry sweep through the porous foam. However, severe cracking is clearly seen on the surface of the cell because of mismatching of thermal expansion coefficient (TEC) during sintering. Therefore, the cell with three cathode layers having TEC gradient (13.83, 13.62 and 13.40 ppmK-1) and %weight content of cermet gradient (70%, 60% and 50%weight) is fabricated. Heating rate and steps are controlled at 0.5˚C/min (600 ˚C), 3˚C/min (800 ˚C) and 1˚C/min (1,300˚C, 4 h) to burn off additives before sintering