Theoretical insight into the electronic, optical, and photocatalytic properties and quantum capacitance of Sc2CT2 (T = F, P, Cl, Se, Br, O, Si, S, OH) MXenes

MXenes are excellent electrode materials and have superior photocatalytic activity. The electronic properties, optical properties, photocatalytic activity and quantum capacitance of Sc2CT2 (T = F, P, Cl, Se, Br, O, Si, S, OH) monolayers are explored by first-principles calculations. All the possible configurations are considered. The results indicate that the introduction of F, Cl, Br, S groups results in the metal-to-indirect-semiconductor tran-sition, while the introduction of O, OH groups makes the metal-to-direct-semiconductor transition. Sc2C(OH)2 monolayer can be applied in optoelectronic fields to improve its power efficiency because of low work function. The analysis of optical properties indicates that Sc2CT2 (T = P, Si) monolayers show the strong absorption performance in infrared region, while Sc2CT2 (T = F, Cl, Se, Br, O, S, OH) monolayers show the strong absorption performance in ultraviolet region. When compared with other systems, Sc2CT2 (T = O, S) monolayers have the better photocatalytic activity within the pH scope of 7.52-14 and 0-0.2, respectively. Our research also indicates that Sc2CT2 (T = F, P, Cl, Se, Br, O, S, OH) monolayers are potential cathode materials in aqueous and ionic/ organic systems.