Exsolution of nickel nanoparticles at the surface of a conducting titanate as potential hydrogen electrode material for solid oxide electrochemical cells

A new La0.5Sr0.5Ti0.75Ni0.25O3 (LSTN25) titanate was proposed as a hydrogen electrode for Solid Oxide Cells (SOCs) with electrochemical performance given by Ni nanoparticles exsoluted at the surface of a conducting oxide. As only in-situ reduction at 800 °C has been proposed in literature to perform Ni exsolution, the reduction at higher temperature of the LSTN25 compound was also considered in this work. The high-temperature treatment led to the precipitation of Ni nanoparticles evidenced by TEM observation and to an improved electrical conductivity that may be due to the formation of a sufficiently high concentration of Ti3+. Electrochemical study of symmetrical cells tested in H2/H2O (97/3) showed a promising performance, with a polarization resistance of 0.55 Ω cm2 at 800 °C and 0.46 Ω cm2 after a thermal treatment in air that simulates the air electrode sintering.

► New titanate, La0.5Sr0.5Ti0.75Ni0.25O3, was proposed as hydrogen electrode for SOCs.
► Ni exsolution was studied via reduction in situ at 800 °C and at higher temperature.
► Both reduction and pre-reduction lead to precipitation of Ni nanoparticles.
► After pre-reduction conductivity was improved probably due to the formation of Ti3+.
► Polarization resistance was measured equal to 0.56 Ω cm2 at 800 °C in H2/H2O (3%).