  One of the most explored MXenes is the Ti3C2Tx, where Tx is designated to
inherently formed termination species. Among many applications, Ti3C2Tx is an
excellent material for energy storage, energy converting, and CO2-capturing
devices. However, active sites for adsorption and surface reactions on the
Ti3C2Tx-surface are still open questions to explore, which have implications
for preparation methods when to obtain correct and optimized surface
requirements. Here we use X-ray photoelectron spectroscopy to study adsorption
of common gas molecules such as H2, CO2, and H2O, which all might be present in
energy storage, energy converting, and CO2-capturing devices based on 2D flakes
of Ti3C2Tx. The study shows that H2O, with a strong bonding to the Ti-Ti
bridge-sites, can be considered as a termination species. An H2O terminated
Ti3C2Tx-surface restricts the CO2 adsorption to the Ti on-top sites and reduces
the ability to store positive ions, such as Li+ and Na+. On the other hand, an
H2O terminated Ti3C2Tx-surface shows the capability to split water. The study
further shows that H2 has the ability to remove F at moderate temperatures. The
results from this study have implications for correct selection of MXene
preparations and the environment around the MXene in different implementations.
