Improved mesoporous scaffolds for composite electrodes in solid oxide devices for direct hydrogen production

The utilization of nanocomposite electrodes has been proven as an effective approach to enhance the performances of Solid Oxide Cell (SOC) devices. Among different strategies, the employment of mesoporous materials synthetized by hard-template methods came to the fore because of their elevated degree of porosity and the high level of provided percolation. Moreover, their use mitigates the formation of high current-density paths. Nano casting method allows the fabrication of high ordered microstructures presenting good thermal distribution through the electrode. Gadolinium-doped ceria (CGO - Ce1-xGdxO2-x/2) is one of the state-of-the-art materials on SOC devices [1] due to its remarkable ionic conductivity and its high thermochemical stability. CGO is employed as a porous backbone and is typically infiltrated by perovskite catalysts such La1-xSrxCoO3-δ (LSC), La1-xSrxMnO3 (LSM) or La1-xSrxCo1-yFeyO3-δ (LSCF) [2] for the fabrication of SOC oxygen electrodes. The large utilization of mesoporous CGO backbones have been limited so far by: i) thermal stability during the processing steps of the device and ii) silica contamination coming from the template, which could inhibit the ionic conductivity of the material and affect the final performances [3]. A two-fold route was developed for overcoming such drawbacks by ex-situ chemical removal of the residual SiO2 and by decoration with cobalt oxide (sintering aid) and presented in a dedicated study [4]. The CGO mesoporous powders were used as backbone for the oxygen electrode fabrication in a complete SOC, which was electrochemically tested in SOFC and SOEC configuration, showing high performances (1.35 W cm−2 at 0.7 V and an injected current of 1.30 A cm−2 at 1.3 V, respectively, at T = 750 °C) overcomes state-of-the-art benchmark cells with similar configuration and sparks the interest towards novel strategies based on ceramic nanocomposites for SOC application [4]. In this contribution is reported the electrochemical characterization by impedance spectroscopy after a durability test made on this device for 1000 h at 750 °C applying a current density of 0.5 A cm-2. Such test showed a degradation rate of ≈125 mV kh-1