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

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.