Processing Nano-YSZ in Solid Oxide Fuel Cells: The Effect of Sintering Atmosphere on Thermochemical Stability

Abstract

The thermochemical stability of nanoscale yttria-stabilized-zirconia (nYSZ), processed via in situ carbon templating, was studied between 850 • C-1350 • C in four sintering atmospheres: Ar, N 2 , H 2 , and humidified H 2 . The in situ carbon templating method generates nanoscale ceramic particles surrounded by an amorphous carbon template upon sintering. The carbon template is subsequently removed by low temperature oxidation, leaving behind nanoscale ceramic particles. In Ar and H 2 , a ZrC impurity formed at temperatures ≥1150 • C. In humidified H 2 , either a ZrC impurity formed or the carbon template oxidized. In N 2 , ZrC was not observed over the temperature range studied and the carbon template was preserved. After carbon template removal, the nYSZ surface areas were high for Ar, H 2 , and N 2 : 55-99 m 2 • g −1 . For humidified H 2 , nYSZ surface area decreased as the carbon template was lost. Finally, nYSZ, processed in N 2 at 850 • C and 1250 • C, was integrated into symmetric YSZ-Lanthanum Strontium Ferrite (YSZ-LSF) cathode cells. The addition of nYSZ decreased cathode non-ohmic resistance, at 550 • C in air, by 40% and 27% for nYSZ processed at 850 • C and 1250 • C, respectively. This work demonstrates that N 2 is a thermochemically stable atmosphere for in situ carbon templating and that the resulting nYSZ considerably improves electrode performance.

Enhancing Activity, Charge Transport, Power Production, and Stability of Commercial Solid Oxide Fuel Cells with Yttria-Stabilized Zirconia Nanoparticles

“…This method produces high surface area mixedmetal-oxides by heating hybrid inorganic-organic materials to 850 °C-1350 °C in nitrogen or argon followed by oxidation at 700 °C in air. [17][18][19] As stated previously, nanoYSZ is a pure oxygen ion conductor and has virtually no electrocatalytic activity for the oxygen reduction reaction. Similar to reports on infiltrated MIECs, the addition of nanoYSZ lowered the cathode reaction impedance by 40%.…”

“…Material preparation.-NanoYSZ was generated via an in situ carbon templating processing method, which has also been shown to generate ultra-high surface area particles for other SOFC relevant mixed-metal-oxides including GDC, LSCF, and strontium titanate. [17][18][19][20] The in situ carbon templating method involves two steps. First, a hybrid inorganic-organic material containing stoichiometric amounts of metal components of the desired mixed-metaloxide is heat treated at 850 °C-1350 °C in an inert atmosphere such as nitrogen or argon.…”

Effect of Sintering Under CO+N ₂/H ₂ and CO ₂+Air Atmospheres on the Physicochemical Features of a Commercial Nano-YSZ

“…In addition, porous Ni-YSZ composites are widely used as fuel electrodes [1][2][3]. Processing methods of anodes for fuel cells that use in situ carbon templating have been developed in order to generate a porous structure [4,5]. In this type of route, carbon usually surrounds the ceramic particles preventing them from sintering into larger particles and is burned away in air.…”

“…In this type of route, carbon usually surrounds the ceramic particles preventing them from sintering into larger particles and is burned away in air. Impurity phases such as monoclinic zirconia and ZrC can be formed during the process [5]. Despite those studies, the effect of related atmospheres generated when C templating is used during sintering of Ni-YSZ on the physicochemical characteristics of nano-zirconia has attracted until now little attention [6].…”

Lowering the Impedance of Lanthanum Strontium Manganite-Based Electrodes with Lanthanum Oxychloride and Lanthanum Scavenging Chloride Salts

“…The nano-YSZ was generated by a novel processing technique referred to as in situ carbon templating. [11][12][13][14][15][16] The processing method involves heating an inorganic-organic hybrid material containing zirconium and yttrium in an inert atmosphere, forming YSZ nanoparticles embedded in amorphous carbon. Subsequently, the amorphous carbon is burned off at a low temperature, 550 °C-700 °C, leaving behind the YSZ nanoparticles.…”