Hydrothermal Synthesis of Graphene-TiO₂ Nanotube Composites with Enhanced Photocatalytic Activity

TLDR

The authors aim to synthesize TiO₂ nanotube/reduced graphene oxide composites via an alkaline hydrothermal route that produces high‑surface‑area, small‑diameter TNTs while converting GO to hGO without strong reducing agents, proposing this as a strategy for other carbon‑based TiO₂ nanotube photocatalysts. They decorate GO with TiO₂ nanoparticles, then hydrothermally convert the nanoparticles into ~9 nm TNTs on hGO, simultaneously reducing GO to hGO, and confirm the graphene nature of hGO by XRD, Raman, FTIR, and XPS, subsequently testing the composites’ photocatalytic activity for malachite green degradation. The hGO‑TNT composites show that a 10 % hGO loading yields a three‑fold increase in photocatalytic efficiency over pure TNTs, while higher hGO content diminishes activity, and hGO itself exhibits a ~70 % reduction in oxygenated species compared to GO.

Abstract

In this study, TiO2 nanotube (TNT)/reduced graphene oxide (hGO) composites were prepared by an alkaline hydrothermal process. This was achieved by decorating graphene oxide (GO) layers with commercially available TiO2 nanoparticles (P90) followed by hydrothermal synthesis, which converts the TiO2 nanoparticles to small diameter (∼9 nm) TNTs on the hGO surface. The alkaline medium used to synthesize the TNTs simultaneously converts GO to deoxygenated graphene oxide (hGO). Compared to GO, the hGO has a ∼70% reduction of oxygenated species after alkaline hydrothermal treatment. The graphene nature of hGO in the composites was confirmed by X-ray diffraction (XRD), Raman, FTIR, and X-ray photoelectron spectroscopy (XPS) analysis. The photocatalytic performance of the hGO-TNT composites was evaluated for the photodegradation of malachite green. It was found that the ratio of hGO to TNT in the composites significantly affects the photocatalytic activity. Higher amounts of hGO in hGO-TNT composites showed lower photocatalytic activity than pure TNTs. The composite with 10% hGO showed the highest photocatalytic activity, with a 3-fold enhancement in photocatalytic efficiency over pure TNTs. It is expected that the synthesis of "high surface area-small diameter" TiO2 nanotubes and simultaneous conversion of GO to graphene like hGO "without using strong reducing agents" could be a promising strategy for preparing other types of carbon based TiO2 nanotube composite photocatalysts.