Synergistic effect of interstitial C doping and oxygen vacancies on the photoreactivity of TiO2 nanofibers towards CO2 reduction

TiO2 nanofiber membranes were prepared by calcinating the electrospun TiO2 nanofibers precursor. Sample calcined at 400 °C (T400) exhibited high CO2 to CH4 conversion efficiency (55.17 μmol·g−1·h−1) and electron selectivity (98.3%) under simulated sunlight. In-situ DRIFTS and the calculated Gibbs free energy revealed CO* to be a major intermediate with the formation of COH* intermediate being the rate-limiting step. The considerable CO2 photoreduction behavior obtained on T400 sample can be attributed to the following causes: (1) the existence of surface OVs gives the change in electronic structure by upshifting CB position to be capable of CO2 photoreduction; (2) the surface Ti terminals acted as reaction sites, resulting in the accumulation of CO* intermediates to continually produce CH4 with the support of sufficient electrons. These results lay the foundation for advancing the mechanistic insight on CO2 photoreduction and its selectivity to CO2 to CH4.