Functional Group Effects on the Photoelectronic Properties of MXene (Sc(2)CT(2), 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 Sc(2)CT(2) (T = -O, -OH, -F) MXenes. For all geometries of the Sc(2)CT(2) MXenes, the geometry I of Sc(2)CT(2), which has the functional groups locating above the opposite-side Sc atoms, are lowest-energy structure. Accordingly, the energetically favorable Sc(2)CF(2)-I, Sc(2)CO(2)-I and Sc(2)C(OH)(2)-I were selected for further evaluation of the photocatalytic activities. We found that the Sc(2)CO(2)-I is metallic, while Sc(2)CF(2)-I and Sc(2)C(OH)(2) are semiconductors with visible-light absorptions and promising carrier mobilities. Compared with the Sc(2)C(OH)(2)-I, the Sc(2)CF(2)-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.