The co-electrolysis of CO2-H2O to methane via a novel micro-tubular electrochemical reactor

Efficient and direct conversion of CO 2 to hydrocarbons through electrolysis is a promising approach for energy storage and CO 2 utilization. In this study, high temperature co-electrolysis of H 2 O-CO 2 and low temperature methanation processes are synergistically integrated in a micro-tubular reactor. The temperature gradient along the micro-tubular reactor provides favorable conditions for both the electrolysis and methanation reactions. Moreover, the micro-tubular reactor can provide high volumetric factor for both the electrolysis and methanation processes. When the cathode of the micro-tubular reactor is fed with a stream of 10.7% CO 2 , 69.3% H 2 and 20.0% H 2 O, an electrolysis current of −0.32 A improves CH 4 yield from 12.3% to 21.1% and CO 2 conversion rate from 64.9% to 87.7%, compared with the operation at open circuit voltage. Furthermore, the effects of the inlet gas composition in the cathode on the CO 2 conversion rate and the CH 4 yield are systematically investigated. Higher ratio of H : C in the inlet results in higher CO 2 conversion rate. Among all the cases studied, the highest CH 4 yield of 23.1% has been achieved when the inlet gas in the cathode is consisted of 21.3% CO 2 , 58.7% H 2 and 20.0% H 2 O with an electrolysis current of −0.32 A. Efficient and direct conversion of CO 2 to hydrocarbons through electrolysis is a promising approach for energy storage and CO 2 utilization.