Synthesis, characterization, and performance evaluation of multilayered photoanodes by introducing mesoporous carbon and TiO(2) for humic acid adsorption

Nanostructured photoanodes were prepared via a novel combination of titanium dioxide (TiO(2)) 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 TiO(2), TiO(2)/C/TiO(2), TiO(2)/C/C/TiO(2), and TiO(2)/C/TiO(2)/C/TiO(2) 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 TiO(2)/C/C/TiO(2) under an illumination intensity of 100 mW cm(−2) from a solar simulator. The highest value of surface roughness was measured for a TiO(2)/C/C/TiO(2) 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 TiO(2)/C/TiO(2) 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 TiO(2) 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 TiO(2)/C/C/TiO(2) 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.