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

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 R_p of the symmetric cell with Cr₂O₃-coated Ni/YSZ is smaller than the R_p 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.