Synthesis, characterization, and performance evaluation of multilayered photoanodes by introducing mesoporous carbon and TiO2 for humic acid adsorption

Abstract

Soraya Hosseini,1 Hossein Jahangirian,2 Thomas J Webster,2 Salman Masoudi Soltani,3 Mohamed Kheireddine Aroua1 1Department of Chemical Engineering, University of Malaya, Kuala Lumpur, Malaysia; 2Department of Chemical Engineering, Northeastern University, Boston, MA, USA; 3Department of Chemical Engineering, Imperial College London, South Kensington Campus, London, UK Abstract: Nanostructured photoanodes were prepared via a novel combination of titanium dioxide (TiO2) nanoparticles and mesoporous carbon (C). Four different photoanodes were synthesized by sol–gel spin coating onto a glassy substrate of fluorine-doped tin oxide. The photocatalytic activities of TiO2, TiO2/C/TiO2, TiO2/C/C/TiO2, and TiO2/C/TiO2/C/TiO2 photoanodes were evaluated by exposing the synthesized photoanodes to UV–visible light. The photocurrent density observed in these photoanodes confirmed that an additional layer of mesoporous carbon could successfully increase the photocurrent density. The highest photocurrent density of ~1.022 mA cm-2 at 1 V/saturated calomel electrode was achieved with TiO2/C/C/TiO2 under an illumination intensity of 100 mW cm-2 from a solar simulator. The highest value of surface roughness was measured for a TiO2/C/C/TiO2 combination owing to the presence of two continuous layers of mesoporous carbon. The resulting films had a thickness ranging from 1.605 µm to 5.165 µm after the calcination process. The presence of double-layer mesoporous carbon resulted in a 20% increase in the photocurrent density compared with the TiO2/C/TiO2 combination when only a single mesoporous carbon layer was employed. The improved performance of these photo­anodes can be attributed to the enhanced porosity and increased void space due to the presence of mesoporous carbon. For the first time, it has been demonstrated here that the photoelectrochemical performance of TiO2 can be improved by integrating several layers of mesoporous carbon. Comparison of the rate of removal of humic acid by the prepared photoanodes showed that the highest performance from TiO2/C/C/TiO2 was due to the highest photocurrent density generated. Therefore, this study showed that optimizing the sequence of mesoporous carbon layers can be a viable and inexpensive method for enhanced humic acid removal. Keywords: renewable energy, photocatalysis, mesoporous carbon, TiO2 nanoparticle, multilayer photoelectrode, humic aci