Coral-Shaped TiO2-δ Decorated with Carbon Quantum Dots and Carbon Nanotubes for NO Removal

Coral-like TiO2-delta] microstructures with high surface area were synthesized by a simple hydrothermal method, followed by thermal treatment in a N-2 atmosphere. The introduction of oxygen vacancies (OVs) to TiO2 significantly improved light absorption and inhibited the recombination of photogenerated charge carriers. Then, multiwalled carbon nanotubes (CNTs) and N-doped carbon quantum dots (N-CQDs) were decorated on the surface of coral-like TiO2-delta microstructures. The CNTs could greatly improve the separation and transfer efficiency of photogenerated charge carriers, while the N-CQDs could further extend light absorption to longer wavelengths, including the IR region. According to the results of electron spin resonance (ESR) spectroscopy, the introduction of OVs to TiO2-delta and surface modification with CNTs and N-CQDs promoted the generation of O-center dot(2)- and (OH)-O-center dot active species. The formation of O-center dot(2)- and (OH)-O-center dot active species on the surface of TiO2-delta/CNTs/N-CQDs played an important role in the deep oxidation and selective conversion of NO into nitrate. Density functional theory calculations revealed the adsorption and reaction sites for H2O and O-2 separately in space over the surface of TiO2-delta CNTs/N-CQDs. Namely, the reaction sites of H2O and O-2 are on the surface of TiO2- delta and CNTs, respectively. The electron transfer from TiO2-delta to CNTs was further verified through the differential charge density. This study demonstrates a straightforward approach for designing full-spectrum-responsive photocatalysts with high efficiency, stability, and selectivity for NO removal.

Automated summary

By introducing oxygen vacancies to TiO2-delta and decorating with CNTs and N-CQDs, the generation of active species promoted deep oxidation and selective conversion of NO into nitrate. The adsorption and reaction sites for H2O and O-2 separately in space over the surface of TiO2-delta CNTs/N-CQDs were revealed through density functional theory calculations, demonstrating high efficiency and selectivity for NO removal.