In Situ Loading of NCQDs on TiO ₂ via Dual-Role Pyridine-Mediated Spray Flame Synthesis for Enhanced CO ₂ Photoreduction

Flame spray pyrolysis (FSP) holds great potential for the scalable fabrication of functional nanomaterials. However, the rational utilization and controllable regulation of carbon species during combustion remain a significant challenge. Herein, we present a novel in situ strategy to construct nitrogen-doped carbon quantum dots (NCQDs) on TiO2 by introducing pyridine as a dual C/N source into FSP. The high-temperature (Tmax ∼ 2033 K) and millisecond-scale rapid reaction environment restricts the complete combustion of pyridine, facilitating the transformation of residual carbon species into graphitized NCQDs. Characterization reveals that nitrogen is incorporated primarily as pyrrolic and graphitic N. The resulting NCQDs/TiO2 heterojunction demonstrates enhanced CO2 photoreduction performance. Mechanistically, NCQDs not only serve as electron reservoirs to facilitate charge extraction and prolong carrier lifetime but also provide N-doping-derived basic sites that enhance CO2 adsorption. Furthermore, NCQDs accelerate the activation of CO2 and H2O molecules, generating abundant active intermediates for efficient catalysis. This work introduces an innovative strategy for constructing high-performance photocatalysts, providing support for the efficient utilization of carbon species in flame synthesis.