Functional Group Effects on the Photoelectronic Properties of MXene (ScCT, T = O, F, OH) and Their Possible Photocatalytic Activities.

In view of the diverse functional groups left on the MXene during the etching process, we computationally investigated the effects of surface-group types on the structural, electronic and optical properties of ScCT (T = -O, -OH, -F) MXenes. For all geometries of the ScCT MXenes, the geometry I of ScCT, which has the functional groups locating above the opposite-side Sc atoms, are lowest-energy structure. Accordingly, the energetically favorable ScCF-I, ScCO-I and ScC(OH)-I were selected for further evaluation of the photocatalytic activities. We found that the ScCO-I is metallic, while ScCF-I and ScC(OH) are semiconductors with visible-light absorptions and promising carrier mobilities. Compared with the ScC(OH)-I, the ScCF-I has not only more suitable band gap (1.91 eV), but also the higher redox capability of photo-activated carriers, which should have better photocatalytic performance.