Predicting a new graphene derivative C3H as potential photocatalyst for water splitting and CO2 reduction

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 sp² 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 10³ cm² ⋅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.