Carbon Dioxide Reduction-Oxygen Production Tandem Reactor: Development of the Electrolysis Part and Full-scale Testing

JAXA has developed a tandem reactor for carbon dioxide reduction-oxygen production intended for air revitalization systems in future manned space missions. A prototype of this tandem reactor has previously demonstrated oxygen generation for a four-crew-member scale followed by CO2 methanation in a full-scale model test. This experiment revealed a high hydrogen content in the oxygen produced at the anode side, attributed to hydrogen crossover through the polymer electrolyte membrane (PEM). Two approaches were considered to reduce the hydrogen concentration in oxygen: substituting the PEM and the catalyst on the anode side. Consequently, a full-scale test of a modified 15-cell stack demonstrated a significant improvement, reducing the H2/O2 ratio to approximately 0.03%.