CO2 concentration effects on CO2/H2O co-electrolysis in a solid oxide electrolysis button cell

The influence of CO₂ gas concentration on the co-electrolysis performance of an electrolyte-supported button cell (NiO-YSZ/NiO-SDC/ScSZ/LSCF-GDC/LSCF) was investigated. At 800 ^oC/1.5V, the interfacial polarization resistance (R_p) values for 10%CO₂/15%H₂O and 30%CO₂/15%H₂O are 7.19 and 26.91 Ω.cm², respectively. CO₂ gas concentration significantly affects the R_p value. Gas diffusion resistance is dominant in the overall polarization resistance. As the CO₂ concentration increases (10%→30%), H₂ consumption increases, indicating RWGS dominance. For 30% CO₂/15% H₂O, CO₂ out is slightly more than the input value due to the WGS and Boudouard reactions. As the applied voltage value increases from OCV, the H₂ residue increases. H₂O and CO₂ co-electrolysis occurs at 1.5 V. The post-test XRD and Raman spectra results show NiO reduction and metallic Ni appearance. The post-test FE-SEM micrographs show no delamination at the air electrode/electrolyte interface, and carbon deposition is observed in the composite fuel electrode layer.