▎ 摘　　要

A new graphene derivative C3H monolayer is identified theoretically by swarm-intelligence structural search and first-principles calculations. The single-layer C3H with a planar conformation is built by annular C18H6 units and shows high thermodynamic stability, due to the sp(2) hybridization between C atoms. It is a direct bandgap semiconductor with a quasi-particle (QP) gap of 3.44 eV. The valence band maximum (VBM) and conduction band minimum (CBM) are mainly contributed by p(z) orbital of C atom. The C3H monolayer has both high electron and hole mobilities in the order of magnitude of 10(3) cm(2) .V-1 .s(-1). Furthermore, the optical bandgap of C3H is 2.47 eV with a high exciton binding energy of 0.97 eV. On the other hand, the energy level positions of VBM and CBM straddle the redox potential of water splitting and CO2 reduction, indicating potential photocatalytic activity. All these desirable functional properties of C3H open a wealth of opportunity for applications in electronics, photo-electronics and photocatalyst.