Redox-stable composite electrodes for CH4 conversion reactors based on proton ceramic electrochemical cells

Electrochemical reactors based on proton-conducting ceramic electrolytes show a great potential in the conversion of hydrocarbons by enabling the intensification via the in-situ extraction of the H2 produced. However, non-oxidative operation conditions lead to the progressive coke formation on the catalyst and electrodes and thus, an oxidative regeneration cycle is required to restore the catalyst activity. Consequently, newly redox-stable electrodes are required to enable operation under both non-oxidative H2-extraction and coke-oxidation conditions. Here, four composite materials were investigated as redox-stable electrode backbones for their integration in proton-conducting cells, composed by the proton conductor BaCe0.2Zr0.7Y0.1O3-δ (BCZY27) and La0.85Sr0.15FeO3 (LSF8515), La0.5Sr0.5FeO3 (LSF55), La0.84Sr0.16Cr0.5Mn0.5O3 (LSCM) or La0.8Sr0.2MnO3 (LSM). Chemical compatibility with the electrolyte and electrochemical performance were characterized in the range 500–800 °C. LSCM/BCZY27 and LSM/BCZY27 showed the best performance. The electrode activity was boosted by catalytically activating with Pt and CeO2 nanoparticles while exhibiting outstanding stability upon redox cycling. LSM/BCZY27+Pt/CeO2 showed the lowest polarization resistance, i.e., achieving 0.7 Ω cm2 at 700 °C in 10% CH4 and 9% H2 and 0.14 Ω cm2 in air, revealing a high potential as redox-stable electrode for non-oxidative hydrocarbon conversion in electrochemical reactors.