CO2 capture from air and its conversion to CH4 using dual functional materials supported on high surface area graphite

Several cycles of CO 2 capture from synthetic air containing 400 ppm of CO 2 and subsequent conversion to CH 4 have been performed using dual functional materials consisting of 4 wt% Ru and 10 wt% Ba or Cs supported on a high surface area graphite. The effect of the presence of humidity and the regeneration conditions have been assessed. The presence of moisture in the air enhances CO 2 capture. The capture material is not properly regenerated in the absence of H 2 -containing atmosphere or at temperatures below 300 ºC. The exhaustive characterization by XRD, XPS, TEM and temperature programmed reduction and reaction allowed to shed some light about the reasons of the different behavior of Ba and Cs based dual functional materials. Cs is more efficiently utilized than Ba, providing higher CO 2 capture capacities (0.44 mmol g −1 ) and CH 4 productivity (0.41 mmol g −1 ). The outperformance of Cs is attributed to the more homogeneous and better dispersed species which are regenerated at lower temperatures. • Cyclic direct air capture and conversion using Ru-(Ba or Cs) on HSGA graphite. • The presence of moisture in the air enhances CO 2 capture. • The material is not regenerated in the absence of H 2 or below 300 ºC. • Cs is more efficient than Ba, providing higher CH 4 productivity (0.41 mmol g −1 ). • The carbonated species formed with Cs are more homogeneous and better dispersed.