Direct air capture of Na8Ti5O14 in the presence of water vapor at room temperature

Sodium pentatitanate, Na8Ti5O14, was novelly applied to direct air capture at room temperature in the presence of water vapor. Na8Ti5O14 was synthesized by heating a mixture of Na2CO3 and TiO2 at 700 °C and then the CO2 absorption characteristics under airflow in the presence of water vapor of the synthesized Na8Ti5O14 were investigated. Thermogravimetry and mass spectroscopy clarified that Na8Ti5O14 had a higher CO2 absorption property in the presence of water vapor, compared to other sodium titanates, such as Na2Ti3O7, Na2Ti6O13, and Na4Ti5O12, indicating that Na8Ti5O14 is a unique CO2 absorbent material in ambient air. Na8Ti5O14 absorbed CO2 in the range of relative humidity of 40 to 75 % at room temperature to produce sodium carbonates. It was also confirmed that Na8Ti5O14 was reproduced by releasing CO2 and H2O below 250 °C.