64 / 2021-11-29 23:56:03

Novel Cu-based perovskites for Solid Oxide Cells

Cu-based oxide,perovskite,oxygen electrode,electrocatalytic activity,reversible SOC

Mineral Materials and Advanced Energy Materials > 8. New Energy Materials

Reversible solid oxide cells can work as electricity and heat generators, but also as electrolyzers, generating hydrogen fuel when surplus electrical energy is available. Currently, Co-based perovskites are usually adopted for preparation of their oxygen electrode, but cobalt is toxic, expensive, as well as its resources are limited. In this work we show the development of high Cu content electrode compounds from the proposed RE_1-xA_xTM_1-yCu_yO_3-δ (RE: selected rare-earth elements, A: selected alkaline-earth metals, TM: selected 3d metals) group, in which Co was fully replaced or its content was largely limited. The studied materials were synthesized by sol-gel and solid-state methods, the phase composition and crystal structure were confirmed by X-ray diffraction at room and high temperatures. Physicochemical properties, including thermal expansion, oxygen content, electrical conductivity and catalytical activity, were studied by dilatometry, iodometric titration, thermogravimetry, and 4-probe electrical conductivity measurements, respectively. Screen-printing method was used for the preparation of the RE_1-xA_xTM_1-yCu_yO_3-δ electrode layers. The polarization resistance was evaluated in symmetrical cells. Button-type full cells were constructed using thin La_0.8Sr_0.2Ga_0.8Mg_0.2O_3-δ electrolyte, RE_1-xA_xTM_1-yCu_yO_3-δ oxygen electrode and Ni-Ce_0.8Gd_0.2O₂ cermet anode. It was found that copper allows to decrease the thermal expansion, while the oxides show suitable stability at high temperatures, as well as high mixed electrical conductivity. Low electrode polarization values were obtained, below 0.1 Ω cm² at 650 °C, which enabled to achieve power density outputs exceeding 250 mW cm^-2 at the same temperature. Good properties were also achieved in the reversed operation. The results clearly indicate that copper-based perovskites show suitable electrocatalytic activity, and Cu can be used to replace cobalt for the preparation of the effectively-working oxygen electrode materials.