Ta[sbnd]O[sbnd]C chemical bond enhancing charge separation between Ta⁴⁺doped Ta₂O₅quantum dots and cotton-like g-C₃N₄

We successfully synthesized a novel Ta⁴⁺self-doped Ta₂O₅quantum dots and the self-doped Ta₂O₅quantum dots modified cotton-like g-C₃N₄nanosheet (TCN) by vapor hydrolysis reaction and calcining treatment. The as-prepared Ta₂O₅showed excellent visible light response from 400 to 800 nm, mainly because the formation of Ta⁴⁺species, which was confirmed by EPR and XPS technology. The estimated bandgap of the self-doped Ta₂O₅was ∼2.78 eV, which was much lower than that of the commercial Ta₂O₅(∼4.0 eV), and the visible light photocatalytic activity of the self-doped Ta₂O₅for hydrogen production was about 7.98 μmol g⁻¹ h⁻¹. The photocatalytic activity of TCN photocatalyst for hydrogen production and RhB degradation was highly enhanced under visible light irradiation compared with those of g-C₃N₄and the self-doped Ta₂O₅, indicating the higher charge separation efficiency, which was further confirmed by the photocurrent transient response, electrochemical impendence spectra and PL emission spectra. And the hydrogen evolution rate and the degradation rate constant for RhB degradation of TCN photocatalyst could reach 624.99 μmol g⁻¹ h⁻¹and 0.1512 min⁻¹, which were about 3.7 and 11.9 times higher than those of pure g-C₃N₄, and 78.29 and 283.78 times higher than those of the self-doped Ta₂O₅, much higher than those of the simple physical mixture. The active species trapping experiment of TCN photocatalyst showed that RhB degradation was mainly attributed to the direct hole oxidation. Besides, the XPS results further confirmed that Ta[sbnd]O[sbnd]C chemical bond was formed between the as-prepared Ta₂O₅and cotton-like g-C₃N₄. It was the strong synergistic interactions of Ta[sbnd]O[sbnd]C chemical bond and Ta⁴⁺defect energy level that highly enhanced the photocatalytic activities of TCN catalyst for the hydrogen production and RhB degradation.