RESUMO
The application of double perovskite cobaltites BaLnCo2O6-δ (Ln = lanthanide element) in electrochemical devices for energy conversion requires control of their properties at operating conditions. This work presents a study of a series of BaLnCo2O6-δ (Ln = La, Pr, Nd) with a focus on the evolution of structural and electrical properties with temperature. Symmetry, oxygen non-stoichiometry, and cobalt valence state have been examined by means of Synchrotron Radiation Powder X-ray Diffraction (SR-PXD), thermogravimetry (TG), and X-ray Absorption Spectroscopy (XAS). The results indicate that all three compositions maintain mainly orthorhombic structure from RT to 1000 °C. Chemical expansion from Co reduction and formation of oxygen vacancies is observed and characterized above 350 °C. Following XAS experiments, the high spin of Co was ascertained in the whole range of temperatures for BLC, BPC, and BNC.
RESUMO
Hydrogen production from water electrolysis is a key enabling energy storage technology for the large-scale deployment of intermittent renewable energy sources. Proton ceramic electrolysers (PCEs) can produce dry pressurized hydrogen directly from steam, avoiding major parts of cost-driving downstream separation and compression. However, the development of PCEs has suffered from limited electrical efficiency due to electronic leakage and poor electrode kinetics. Here, we present the first fully operational BaZrO3-based tubular PCE, with 10 cm2 active area and a hydrogen production rate above 15 Nml min-1. The novel steam anode Ba1-xGd0.8La0.2+xCo2O6-δ exhibits mixed p-type electronic and protonic conduction and low activation energy for water splitting, enabling total polarization resistances below 1 Ω cm2 at 600 °C and Faradaic efficiencies close to 100% at high steam pressures. These tubular PCEs are mechanically robust, tolerate high pressures, allow improved process integration and offer scale-up modularity.