(Invited) Efficient Electrochemical Biogas Reforming with Enhanced Carbon Deposition Resistance of Ni/YSZ Electrode Coated with Chromium Oxide in a Solid Oxide Electrolyzer

Abstract

This work investigates the Ni/YSZ and chromium oxide (Cr2O3) coated Ni/YSZ cathodes as electrodes of solid oxide electrolysers for biogas reforming. XRD, TEM, SEM and XPS confirm the formation of NiCr2O4 on Ni surface for the coated samples while it is in-situ reduced to a core-shell structure with Ni metal coated with Cr2O3. The electrical properties of Ni/YSZ and Cr2O3-coated Ni/YSZ are investigated and correlated to their electrochemical performances. The Rp of the symmetric cell with Cr2O3-coated Ni/YSZ is smaller than the Rp with Ni/YSZ in methane atmosphere. Carbon fibers is observed in the Ni/YSZ electrode, rather than in the Cr2O3 loaded Ni/YSZ electrode after exposing in CH4-CO2 (1:1) atmosphere at 800 °C for 1 h. Electrochemical reforming of dry CH4-CO2 (1:1) mixture is successfully achieved in oxide-ion-conducting electrolysers with Ni/YSZ and Cr2O3-coated Ni/YSZ cathodes, respectively. Moreover, it is found that the coating of Cr2O3 on Ni further improves CH4-CO2 conversion. The higher methane and carbon dioxide conversions has demonstrated the superiority of direct electrochemical reforming compared with the low conversions under open circuit condition in oxide-ion-conducting solid oxide electrolysers.