Flame process constructing CQDs/TiO2-C heterostructure with novel electron transfer channel between internal and external carbon species

Abstract The controllable preparation and rational utilization of carbon species produced in flame process is a meaningful research direction. Herein, a CQDs/TiO2 C heterostructure coupling with multi-carbon species was developed in flame process. In the millisecond-level reaction process, part of the residual carbon formed by the incomplete combustion of ethanol penetrates the lattice of TiO2, forming interstitial C (Ci) and substituent C (Cs), and the remaining amorphous carbon quantum dots (CQDs) are adsorbed on the surface of TiO2. In-situ temperature-programmed X-ray photoelectron spectroscopy (In-situ TPXPS) combined with various characterizations proved that the CQDs/TiO2 C heterostructure was successfully constructed in the flame process (the atomic ratio of the two C species was close to 1:1). The carbon species lead to the reduction of the band gap of the targeted material from 2.8 eV to 2.73 eV, meanwhile, the reduction ability is increased by 21.3%. The synergistic effect enhances the separation efficiency of photogenerated electrons by 7 times, achieving a conversion efficiency of 46.21 µmol g−1 h−1 and nearly 100% CO2-to-CO selectivity. Furthermore, the systematic theoretical calculation results visualize this kind of novel electron transfer channel from C to O to CQDs (C O-CQDs).