The comparison of SrTi0.98Nb0.02O3–δ-CeO2 and SrTi0.98Nb0.02O3–δ-YSZ composites for use in SOFC anodes

Abstract

Composites of Nb-doped strontium titanate mixed with yttria-stabilized zirconia or cerium oxide in 50:50, 70:30 and 85:15 weight ratios were evaluated as possible anode/electrolyte interface materials for solid oxide fuel cells in terms of chemical compatibility, electrical conductivity and mechanical properties. It has been shown that composite samples prepared by typical powder-mixing methods remain single-phase up to 1400°C. The electrical conductivity of these composites, regardless of their composition and fabrication conditions, is lower than the conductivity of pure SrTi 0.98 Nb 0.02 O 3-δ , but in most cases sufficient for solid oxide fuel cells anode application. The best properties are found for samples reduced at 1400°C for 10 h in H 2 atmosphere. The observations made by scanning electron microscope suggest that the grains of both phases are well-distributed throughout the whole volume of the investigated samples, and that the composites with CeO 2 better adhere to the electrolyte surface. The electrical results confirm that composites with at most 30 wt % of YSZ/CeO 2 phase fulfill the anode requirements. However, the fuel cell performance tests indicate that the application of composite with CeO 2 results in the lower power density than the application of the composite with YSZ.

Interactions between components of SrTi0.98Nb0.02O3−δ–YSZ and SrTi0.98Nb0.02O3−δ–CeO2 composites

“…However, beside many advantages the Nb‐doped SrTiO 3 shows insufficient ionic conductivity and very low electrocatalytic activity 12. In order to overcome these limitations, composites of Sr(Ti,Nb)O 3 and yttria‐stabilized zirconia (YSZ) or ceria (CeO 2 ) were proposed and investigated 12–20.…”

“…The composites of modified SrTiO 3 and YSZ (denoted as SrTiO 3 –YSZ) offer many advantages in comparison with pure SrTiO 3 ‐based materials, such as improved mechanical connection to YSZ electrolyte 17, 20 and an increase in the triple phase boundary (TPB) length 12, 16. The latter is particularly important in the case of fuel cells applications, because it results in an increased cell performance.…”

“…Particular attention was paid to the properties of Sr(Ti,Nb)O 3 –CeO 2 , which was heat‐treated at high temperature (up to 1400 °C) in a reducing atmosphere. These conditions were chosen on the basis of our previous investigations 20. In the paper 20 it has been shown that such a high temperature of reduction is required to enable sufficient conductivity of SrTiO 3 ‐based composite anode for SOFC.…”

“…These conditions were chosen on the basis of our previous investigations 20. In the paper 20 it has been shown that such a high temperature of reduction is required to enable sufficient conductivity of SrTiO 3 ‐based composite anode for SOFC. Material fabricated in this way can be used, e.g., in an anode‐supported solid oxide fuel cell, where both electrolyte and cathode materials can be deposited using one of the low‐temperature methods (spin‐coating 22, 23, aerosol deposition 24, magnetron sputtering 25, CVD 26, etc.).…”

In situ formation of oxygen vacancy in perovskite Sr0.95Ti0.8Nb0.1M0.1O3 (M = Mn, Cr) toward efficient carbon dioxide electrolysis

“…The metallic behavior of the electronic conductivity adapts well to the strong reducing atmosphere of the cathode under electrolysis conditions. Currently, more attention is being paid to the niobium doping of the B-site, where Nb 5+ partially substitutes Ti 4+ , which significantly improves the electrochemical properties141516. According to a previous report, the electrical conductivity of Sr 0.9 Ti 0.8 Nb 0.2 O 3.00 that was pretreated at 1400°C for 5 h in a H 2 /N 2 atmosphere reached approximately 340 S·cm −1 at 800°C in a reducing atmosphere17.…”