Constructing CeO2/nitrogen-doped carbon quantum dot/g-C3N4 heterojunction photocatalysts for highly efficient visible light photocatalysis.

Abstract

Ternary CeO2/nitrogen-doped carbon quantum dot (NCQD)/graphitic carbon nitride (g-C3N4) heterojunction nanocomposites were prepared by a high-temperature calcination and hydrothermal method and tested for degrading tetracycline (TC) and generating H2. Compared with CeO2 and g-C3N4, the Z-scheme CeO2/NCQDs/g-C3N4 (CSNx, where x represents the amount of CeO2 in wt%) nanoparticles showed a higher TC photodegradation capacity and H2 evolution ability owing to enhanced efficient charge separation and photocatalytic stability. CSN5 showed the best photodegradation activity for TC degradation (100 mL, 20 mg L-1; 100% degradation in 60 min; λ≥ 420 nm) and the highest H2 evolution rate of 1275.42 μmol h-1 g-1 was approximately 3.73- and 32.25-times higher than those of pristine g-C3N4 (341.85 μmol h-1 g-1) and pure CeO2 (39.55 μmol h-1 g-1), respectively. Superoxide (˙O2-) and hydroxyl (˙OH) radicals were also confirmed to be formed on the sample surface for TC photocatalytic degradation. As an electronic medium, NCQDs transferred electrons between the g-C3N4 and CeO2 interface to promote the electron-hole separation. This work affords a helpful perspective for synthesizing efficient charge separation and environmentally friendly photocatalysts by controlling the surface heterostructure.