LAUSR

Broadband light absorption and excellent charge separation/migration efficiency are two important indicators for promising photocatalyst. However, realizing the above two aspects simultaneously is still a challenge. Here, an ultrathin and broadband carbon nitride (UBCN) is synthesized via a short‐time thermal oxidation process. The as‐prepared UBCN exhibits outstanding photocatalytic H2 generation activity (240.60 μmol h−1) under irradiation with λ>400 nm. Moreover, UBCN can work under irradiation with a longer wavelength (λ>500 nm), the corresponding H2 evolution rate is 5.08 μmol h−1, which is 14.8 times higher than that of bulk carbon nitride (Bulk CN). The excellent photocatalytic performance should be credited to the efficient charge separation/migration (the ultrathin structure) and the extended light absorption range. This work provides a simple and convenient strategy to prepare broadband and ultrathin metal‐free photocatalytic materials.