Graphitic carbon nitride/titania nanotube arrays for photoelectrochemical oxidation of methanol under visible light

Abstract

In this study, the fabrication of ordered and vertically oriented titanium dioxide nanotubes (TiO2 NT) array sensitized with graphitic carbon nitride (g-C3N4) nanosheets (g-C3N4 NS/TiO2 NT) was demonstrated as an attractive class of photocatalysts for the visible-light-driven photoelectrochemical oxidation of methanol. The phase and composition of the fabricated g-C3N4 NS/TiO2 NT structures and their precursors were investigated using X-ray powder diffraction (XRD). The morphological and topological characteristics of the prepared materials were studied using scanning electron microscopy (SEM). Raman spectroscopy was employed to study the electronic properties of composite material. Upon the fabrication, characterization, and use of the prepared structures for photoelectrochemical oxidation of methanol under visible-light illumination (50 W halogen lamp, 0.1 M KOH), the g-C3N4 NS/TiO2 NT array showed a significant increase in the photocurrent (96.2 μA cm−2) compared to the TiO2 NT electrode (79 μA cm−2) with 1.2 times enhancement factor. Moreover, decorating the TiO2 NT array resulted in enhanced dark light density that is 8.7 times more than that of the TiO2 NT electrode. The improved photo- and electrochemical properties of the prepared g-C3N4 NS/TiO2 NT could arise from the synergistic effects of g-C3N4 NS decoration and the unique structural properties of the fabricated vertically aligned TiO2 nanotube arrays. The TiO2 NT/g-C3N4 NS composite modified photo-electrode offers 22.55 times the ambient condition “light off” of the TiO2 NT electrode and 2.3 times the irradiated ones. The present study suggests a simple, stable, reusable, and cost-effective approach for the preparation of g-C3N4 NS/TiO2 NT photocatalyst for designing a DMFC.