Mechanism of a reversible CO2 capture monitored by the layered perovskite Li2SrTa2O7

We demonstrate for the first time, a new CO2 capture ability monitored by a Ruddelsden -Popper compound. Under a humid CO2 atmosphere, Li2SrTa2O7 is transformed into LiHSrTa2O7 releasing lithium hydroxide which combined with the atmospheric CO2 leads to Li2CO3. The presence of carbonate is confirmed by IR, thermal analysis coupled with mass spectroscopy and diffraction experiments (X-ray and neutron). The structural study of LiHSrTa2O7 performed with X-ray and neutron diffraction data showed that the structure differs from that of LiHSrTa2O7 obtained by ionic exchange from Li2SrTa2O7 by the Li+/H+ repartition in the interlayer spacing. In the case of the LiHSrTa2O7 studied in this paper, the Li+ and H+ ions are ordered, while in the other form, each cation is unequally distributed on 2 sites. By heating, Li2SrTa2O7 is recovered showing that the CO2 capture is reversible and the cyclability of the CO2 capture has been tested during six cycles.