Malaysian Journal of Analytical Sciences Vol 20 No 1 (2016): 121 - 130

 

 

 

INVESTIGATION ON OPTICAL AND PHOTOELECTROCHEMICAL PROPERTIES OF SELF-ASSEMBLED TITANIA NANOTUBE ARRAYS PREPARED BY ANODIZATION

 

(Penyiasatan Sifat Optik dan Fotoelektrokimia Swahimpunan Nanotiub Titania

Bertatasusunan yang Disediakan Melalui Penganodan)

 

Lim Ying Chin¹*, Zulkarnain Zainal², Mohd Zobir Hussein³, Tan Wee Tee²

 

¹School of Chemistry and Environment, Faculty of Applied Sciences,

Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor, Malaysia

²Department of Chemistry, Faculty of Science

³Advanced Materials and Nanotechnology Laboratory, Institute of Advanced Technology (ITMA)

Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia

 

*Corresponding author: limyi613@salam.uitm.edu.my

 

 

Received: 9 December 2014; Accepted: 16 November 2015

 

 

Abstract

Well ordered and vertically oriented titania nanotubes (TNT) are of great scientific interest due to their high surface area, fewer interfacial grain boundaries and excellent charge transfer between interfaces; all are critical properties in photoelectrochemical and photocatalysis application. In this study, self-assembled TNT electrodes were synthesized by anodization of pure Ti in 0.5 wt.% NH₄F solution (NH₄F/H₂O), in mixture of aqueous-organic solution (NH₄F/H₂O/EG) and in an organic solution (NH₄F/EG). Choice of electrolytic medium has an influence on the crystalline structure, regularity, elemental composition and band gap of TNT. All the samples showed a red shift and stronger absorption in the wavelength between 500-700 nm ascribed to the surface colour and increase crystallinity upon calcination. TNT formed in NH₄F/H₂O solution has the highest direct band gap of 3.34 eV due to quantization effect. From Liner Sweep Photovoltammetry analysis, the lowest photocurrent was recorded for TNT anodized in NH₄F/H₂O and a twofold and fivefold increase on the magnitude of photocurrent was obtained for those formed in NH₄F/H₂O/EG and NH₄F/EG solution, respectively. Hence, highest photoefficiency of 2.79 % was recorded for TNT formed in NH₄F/EG probably due to the formation of longer length tube.

 

Keywords: titania, nanotube, anodization, photoefficiency, band gap energy

 

Abstrak

Nanotiub titanium dioksida yang bertertib rapi dan berorientasi mencancang (TNT) telah menarik perhatian disebabkan luas permukaan yang tinggi, sempadan butiran antara muka yang rendah dan pemindahan cas yang cemerlang di antara muka, yang mana semua ini merupakan ciri – ciri kritikal dalam aplikasi fotoelektrokimia and fotopemangkinan. Dalam kajian ini, swahimpunan TNT telah disintesis melalui penganodan plat titanium tulen dalam larutan 0.5 wt.% NH₄F (NH₄F/H₂O), campuran larutan akua-organik (NH₄F/EG/H₂O) dan larutan organik (NH₄F/EG). Pilihan media elektrolisis memberi kesan ke atas struktur hablur, keteraturan, komposisi unsur dan julang jalur TNT. Semua sampel mempamerkan anjakan merah dan penyerapan yang lebih kuat dalam julat gelombang 500 – 700 nm disebabkan warna permukaan sampel dan peningkatan kehabluran selepas pemanasan. Dari analisis fotovoltammetri pengimbasan linear, TNT yang teranod dalam larutan NH₄F/H₂O mencatatkan fotoarus yang terendah manakala peningkatan lipat ganda dua dan ganda lima dalam magnitud fotoarus boleh didapati untuk TNT yang teranod dalam larutan NH₄F/H₂O/EG dan NH₄F/EG. Oleh yang demikian, TNT yang dibentuk dalam latutan NH₄F/EG mencatatkan kecekapan foto yang tertinggi sebanyak 2.79 % mungkin disebabkan oleh pembentukan tiub yang lebih panjang.

 

Kata kunci: titania, nanotiub, penganodan, kecekapan foto, jalur jurang tenaga

 

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