Na-Based Monolayer Photocatalysts with Extremely High Intrinsic Electric-Field for Water Splitting
Strong built-in electric field, high carrier mobility and wide range of optical absorption are key parameters for photocatalysts used for water splitting. Design and preparation of photocatalyst possessing simultaneously these characteristics have always been a main task in the water splitting field. Here, we put forward a new family of 2D Na-based photocatalysts, NaAB2 (A = Al, Ga, In; B = S, Se, Te) monolayers which may achieve this goal. First-principles calculations show that most of the NaAB2 monolayers are semiconductors with suitable direct bandgap ranging from the visible to near-infrared light, exhibiting good optical absorption. The electron mobilities of NaAB2 monolayers are up to 103 cm2v-1s-1, meaning the rapid migration of electrons can promote photocatalytic overall water splitting. Importantly, the electrostatic potential differences between top surface and bottom surface are larger than 1.23 eV for all studied NaAB2 monolayers, meaning a high intrinsic built-in electric field that makes these Na-based photocatalysts can promote overall water splitting irrespective of their band gaps and band edges. Our studies show that the NaAB2 monolayers may be ideal photocatalysts used for water splitting and may initiate a new round of experimental studies.