Water steam effect during high CO2 chemisorption in lithium cuprate (Li2CuO2) at moderate temperatures: experimental and theoretical evidence

Abstract

Li₂CuO₂ was evaluated as a CO₂ captor at moderate temperatures, using water vapor in the gas flow. Different water vapor sorption experiments were performed using N₂ or CO₂ as carrier gases. If N₂ was used as carrier gas, it was evidenced that Li₂CuO₂ is able to trap water physically and chemically, producing in the second case Li–OH superficial species. Moreover, when CO₂ was used as carrier gas, Li₂CuO₂ continued trapping water, as in the previous case, but in this case CO₂ was mainly trapped, forming Li₂CO₃ and CuO phases. Additionally, the microstructure changes importantly when CO₂ and H₂O are chemically trapped in Li₂CuO₂. Li₂CO₃ and CuO seemed to segregate changing the morphology and the specific surface area. The Li₂CuO₂ sample was able to capture up to 6.7 mmoles of CO₂ per gram of ceramic at 80 °C, a considerably high CO₂ amount. Furthermore, all these experiments were theoretically supported by different thermodynamic calculations. Experimental and theoretical results show that H₂O acts as a catalytic intermediate, diminishing the activation energy of the whole CO₂ chemisorption process. Therefore, the presence of water vapor strongly favored the CO₂ chemisorption on Li₂CuO₂ at moderate temperatures (30–80 °C).