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

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 acid

Acknowledgments

The authors would like to acknowledge High Impact Research (grant number HIR/MOE/ENG59), University of Malaya, Kuala Lumpur, Malaysia, and Northeastern University, Boston, MA, USA, for their earnest cooperation of this research.

Disclosure

The authors report no conflicts of interest in this work.