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 (Rp) 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 Rp 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.