Two-dimensional carbon nitride (2D-C3N4) nanosheets are promising materials in photocatalytic water splitting,but still suffer from easy agglomeration and fast photogenerated electron-hole pairs recombi-nation.To tackle this issue,herein,a hierarchical Nb2O5/2D-C3N4 heterostructure is precisely constructed and the built-in electric field between Nb2O5 and 2D-C3N4 can provide the driving force to separate/trans-fer the charge carriers efficiently.Moreover,the strongly Lewis acidic Nb2O5 can adsorb TEOA molecules on its surface at locally high concentrations to facilitate the oxidation reaction kinetics under irradiation,resulting in efficient photogenerated electrons-holes separation and exceptional photocatalytic hydrogen evolution.As expected,the champion Nb2O5/2D-C3N4 heterostructure achieves an exceptional H2 evolu-tion rate of 31.6 mmol g-1 h-1,which is 213.6 times and 4.3 times higher than that of pristine Nb2O5 and 2D-C3N4,respectively.Moreover,the champion heterostructure possesses a high apparent quantum effi-ciency (AQE) of 45.08％ at λ =405 nm and superior cycling stability.Furthermore,a possible photocat-alytic mechanism of the energy band alignment at the hetero-interface is proposed based on the systematical characterizations accompanied by density functional theory (DFT) calculations.This work paves the way for the precise construction of a high-quality heterostructured photocatalyst with efficient charge separation to boost hydrogen production.