@article {1184, title = {Effect of direct-current operation on the electrochemical performance and structural evolution of Ni-YSZ electrodes}, journal = {Journal of Physics: Energy}, volume = {2}, year = {2019}, month = {12/2019}, pages = {014006}, abstract = {The effect of electrolysis operations on Ni-YSZ fuel electrode stability was studied at different current densities and fuel mixtures during 1000 h life tests. For a typical electrolysis mixture of 50\% H2/50\% H2O and 0.6 A cm-2 current density, cell ohmic resistance values were reasonably stable and no structural changes occurred. However, for more reducing conditions (97\% H2/3\% H2O), increasing the current density above 0.4 A cm-2 increased the ohmic resistance accompanied by significant electrolyte degradation including fracture and void formation at grain boundaries. Numerical analysis was carried out to determine the effective oxygen partial pressure across the electrolyte. The results show that the oxygen partial pressure values at high current density and low steam content may be low enough to reduce zirconia to form a Ni-Zr alloy product, initiating the observed electrolyte structural degradation.}, keywords = {durability, HTE, SOEC, Yttria-stabilized zirconia}, doi = {10.1088/2515-7655/ab59a6}, url = {https://doi.org/10.1088/2515-7655/ab59a6}, author = {Qinyuan Liu and Qian Zhang and Peter W Voorhees and Scott A Barnett} } @article {1062, title = {Cobalt-substituted SrTi0.3Fe0.7O3-δ: a stable high-performance oxygen electrode material for intermediate-temperature solid oxide electrochemical cells}, journal = {Energy \& Environmental Science}, volume = {11}, year = {2018}, month = {07/2018}, pages = {1870-1879}, abstract = {

Published on July 11th, 2018. A key need in the development of solid oxide cells (SOCs) is for electrodes that promote fast oxygen reduction and oxygen evolution reactions at reduced operating temperature (<=700 {\textdegree}C), with sufficient durability to allow operation over desired 40 000 h lifetimes. A wide range of electrode materials have been investigated, with some providing resistance low enough for cell operation below 700 {\textdegree}C, but it is generally found that the electrode performance degrades over time. Here we demonstrate an oxygen electrode material, Sr(Ti0.3Fe0.7-xCox)O3-δ (STFC), that provides a unique combination of excellent oxygen electrode performance and long-term stability. The addition of a relatively small amount of Co to Sr(Ti0.3Fe0.7)O3-δ, e.g., x = 0.07, reduces the electrode polarization resistance by \>2 times. The STFC electrode yields stable performance in both fuel cell and electrolysis modes at 1 A cm-2. The fundamental oxygen diffusion and surface exchange coefficients of STFC are determined, and shown to be substantially better than those of La0.6Sr0.4Co0.2Fe0.8O3-δ, the most widely used SOC oxygen electrode material. While other electrode materials have been shown to exhibit better oxygen transport coefficients than STFC, they do not match its stability.

}, doi = {10.1039/C8EE00449H}, url = {https://pubs.rsc.org/en/content/articlelanding/2018/ee/c8ee00449h}, author = {Shan-Lin Zhang and Hongqian Wang and Matthew Y. Lu and Ai-Ping Zhang and Liliana V. Mogni and Qinyuan Liu and Cheng-Xin Li and Chang-Jiu Li and Scott A. Barnett} }