In this research work, the gas phase CO2 photocatalytic reduction using water as electron donor has been performed using hierarchical assemblies of mesoporous TiO2 1-D nanofibres synthesised by a combination of electrospinning and sol-gel methods. In order to compare the effect of the crystallisation step on oxygen vacancies and conductivity, two different annealing conditions have been undertaken: under a high Ar flow ("TiO2 Fibres-A" sample) and under static Ar ("TiO2 Fibres B" sample). Moreover, these materials have been compared with individualised TiO2 nanoparticles prepared by a sol-gel procedure. CO and H2 are detected as major products with all photocatalysts, with lower amounts of CH4 and CH3OH. The TiO2 nanofibres exhibit better results than the sol-gel photocatalyst, behaviour that may be ascribed to an improved nanocrystals connection, which favours a fast charge transport along the grain boundaries, as measured by electrochemical impedance spectroscopy (EIS). The highest CO2 reduction activity is achieved with the TiO2 Fibres B catalyst, which gives rise to ca. 4 and 2.5 times higher H2 and CO production, respectively, than the TiO2 Fibres-A one. This sample is composed of a mixture of anatase and rutile crystalline phases (80:20), leading to a decrease in the electron-hole recombination rate observed by photoluminescence (PL) measurements.
Reñones, P., Moya, A., Fresno, F., Collado, L., Vilatela, J. J., & De La Peña O’Shea, V. A. (2016). Hierarchical TiO2 nanofibres as photocatalyst for CO2 reduction: Influence of morphology and phase composition on catalytic activity. Journal of CO2 Utilization, 15, 24–31. https://doi.org/10.1016/j.jcou.2016.04.002