Preferentially oriented Ag-TiO2 nanotube array film: An efficient visible-light-driven photocatalyst

Area of Science:

• Materials Science
• Nanotechnology
• Environmental Chemistry

Background:

• Titanium dioxide (TiO2) is a widely used photocatalyst, but its efficiency is limited under visible light.
• Developing novel TiO2 nanostructures with enhanced visible-light photocatalytic activity is crucial for environmental remediation.
• Silver (Ag) doping can improve TiO2's photocatalytic performance through surface plasmon resonance (SPR) and charge carrier dynamics.

Purpose of the Study:

• To fabricate Ag-TiO2 nanotube array films with preferential crystal orientation.
• To investigate the effect of Ag doping on the crystal structure, composition, and microstructure of TiO2 nanotubes.
• To evaluate the photocatalytic activity of Ag-TiO2 nanotube arrays for the reduction of hexavalent chromium (Cr(VI)) under visible light.

Main Methods:

• Fabrication of Ag-TiO2 nanotube array films on ITO glass using magnetron sputtering and anodization.
• Characterization of film composition and microstructure using X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS).
• Photocatalytic activity assessment by monitoring the reduction of Cr(VI) under visible light irradiation.

Main Results:

• Ag doping induced a preferential crystal orientation along the [001] direction in anatase TiO2 nanotubes, attributed to minimized surface energy.
• Ag-TiO2 nanotube arrays exhibited enhanced separation and transfer of photo-induced charge carriers.
• Improved visible light absorption was observed due to SPR effects from Ag and heterojunction formation between TiO2 nanotubes (TNAs) and Ag2O.
• The TNA-3Ag sample demonstrated the highest photocatalytic efficiency, removing 99.1% of Cr(VI) within 90 minutes.

Conclusions:

• The preferential [001] orientation in Ag-TiO2 nanotubes significantly enhances photocatalytic activity.
• Ag doping effectively improves visible light absorption and charge carrier dynamics in TiO2 nanotube arrays.
• Ag-TiO2 nanotube arrays are promising materials for efficient visible-light-driven environmental remediation applications, particularly for Cr(VI) reduction.