Co-electrolysis SOEC and internal reforming SOFC for achieving a carbon-neutral society

Abstract

Solid oxide electrolysis cells (SOECs) can produce carbon monoxide (CO) from carbon dioxide (CO₂) in addition to hydrogen (H₂) from steam using renewable energy sources such as solar and wind power. Methanol (MeOH) and dimethyl ether (DME) are industrially synthesized from syngas (H₂ + CO mixture) with an H₂/CO ratio of 2. Solid oxide fuel cells (SOFCs) can generate power using MeOH and DME in addition to H₂. To achieve a carbon-neutral society, H₂O/CO₂ co-electrolysis SOECs and internal reforming SOFCs using MeOH and DME were investigated using the same negatrode-supported microtubular cells. As a result of quantitative analysis of the gas composition, the H₂/CO ratios of the product gases were identical to the H₂O/CO₂ ratios of the input gases during the co-electrolysis. The gas diffusion resistance increased with decreasing H₂O/CO₂ ratios for co-electrolysis SOECs, and increased with time during co-electrolysis at H₂O/CO₂ = 2 and internal reforming of MeOH and DME. H₂O/CO₂ co-electrolysis SOECs and internal reforming SOFCs using MeOH and DME were successfully operated for 100 h.