Cu nanocrystals enhanced charge separation and transfer in superior thin g-C3N4 nanosheets

Abstract

A two-step thermal condensation approach was developed to fabricate Cu and graphic carbon nitride (g-C3N4) composites. Cu nanocrystals (NCs) with a size range of 2 – 5 nm were embedded in superior thin g-C3N4 nanosheets. Although little amount of Cu NCs was incorporated in g-C3N4 nanosheets, Cu/g-C3N4 composites revealed promoting influence towards photocatalytic H2 generation and photodegradation of pollutions. Namely, the sample 680-Cu0.05% (with Cu of 0.05 wt%) revealed the best photocatalytic performance. Electrochemical test indicates that Cu NCs improve the productivity of the samples. Narrowed band gap in Cu/g-C3N4 composite samples resulted in an expanded photo adsorption in visible light range. The composites also revealed enhanced optical current response and small interfacial charge transport resistances compared with pure g-C3N4 nanosheets (sample Pure-680). The photocatalytic H2 generation rate of the composite was ~ 2790 μmol g−1 h−1, which is 2.3 times of that of Pure-680. The degradation efficiency of rhodamine B using the composite sample reached 95.5 % with a photodegradation rate of 0.0774 min−1 and was described a zero-order kinetics model (C0-C=kt) with a process completing within 35 min. The test of photocatalytic hydrogen evolution stability indicated that it was almost no degradation when using the composite sample after 8 cycles. This work proposes an efficient method to improve the separation and transfer efficiencies of photogenerated carriers in g-C3N4 and could be applied in another two-dimensional composite photocatalysts.