Prof. Yen-Ping Peng
Institute of Environmental Engineering, Sun Yat-sen UniversitySpeech Title: Z-Scheme g-C3N4/TiO2 Nanotube Array Heterojunction for Enhanced Photoelectrochemical Degradation of Trichloroethylene
Abstract: Z-scheme materials have drawn considerable interest for photocatalytic applications. In this study, titanium dioxide nanotube arrays (TNAs) were modified with graphitic carbon nitride (g-C3N4) to form a Z-scheme heterostructure to enhance the photocatalytic degradation of trichloroethylene (TCE). The g-C3N4/TNAs were synthesized via hydrothermal methods, and their properties were characterized by SEM, XRD, UV-vis spectroscopy, photocurrent measurements, electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), and Mott-Schottky analysis. Results of XRD confirmed the formation of anatase TiO2 and the incorporation of g-C3N4, with characteristic peaks at 27.5°. XPS analysis showed shifts in binding energies indicating electron transfer from g-C3N4 to TiO2, confirming the Z-scheme configuration. Photocurrent densities of TNAs, g-C3N4/TNAs-5, and g-C3N4/TNAs-10 were 8.6 μA/cm², 10.6 μA/cm², and 11.7 μA/cm², respectively, under a photoelectrochemical (PEC) system with a 13W LED light source, demonstrating enhanced photoactivity post-modification. In PEC degradation experiments with 100 ppb TCE, g-C3N4/TNAs-5 achieved a 62% degradation rate in 240 minutes, compared to 51% for unmodified TNAs. Purely photocatalytic systems showed that standalone g-C3N4/TNAs exhibited superior degradation efficiency comparable to that of TNAs in the PEC system, indicating that g-C3N4 modification significantly increased photogenerated electron lifetime, thereby enhancing photoelectroactivity. XPS analysis revealed binding energy shifts in Ti 2p and O 1s spectra, suggesting electron donation from g-C3N4 to TiO2, which stabilized Ti bonds and supported the Z-scheme mechanism. Mott-Schottky and UV-vis DRS measurements confirmed the Z-scheme electron transport pathway. Elemental analysis showed an increase in C and N in g-C3N4/TNAs, confirming successful heterojunction formation. In the degradation process, by-products such as cis- and trans-1,2-dichloroethylene emerged, indicating the presence of a novel degradation pathway. This study demonstrates that the hydrothermally synthesized g-C3N4/TNAs Z-scheme heterostructure significantly enhances photocatalytic performance, offering a promising method for the efficient degradation of chlorinated pollutants.