Malaysian Journal of Analytical Sciences Vol 22 No 5 (2018): 750 - 757

EFFECT OF GOLD SOLUTION CONCENTRATION ON THE FORMATION AND PHOTOELECTROCHEMICAL PROPERTIES OF GOLD DEPOSITED TITANIUM DIOXIDE NANOTUBES

(Kesan Kepekatan Larutan Emas Terhadap Pembentukan dan Sifat-Sifat Fotoelektrokimia Nanotiub Titanium Dioksida Terendap Emas)

Siti Sarah Binti Ismail¹, Zainiharyati Mohd Zain¹, Asmaa Kadim Ayal², Lim Ying Chin¹*

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

Universiti Teknologi MARA, 40450 Shah Alam, Selangor, Malaysia

²Department of Chemistry, College of Science for Women,

University of Baghdad, Al-Jadriya Campus, Baghdad, Iraq

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

Received: 29 August 2017; Accepted: 20 June 2018

Abstract

Solar photoelectrochemical (PEC) water splitting for hydrogen production is a clean, eco-friendly, and cost-effective technology that uses solar light as the energy source. Metal oxides, such as TiO₂, are preferable as a photoanode in PEC water splitting as they have relatively high reactivity, stable in aqueous solution, and cheaper than non-oxide semiconductors. However, TiO₂ has a large band gap (3.2 eV) that only allows it to be active upon irradiation with UV light. Thus, gold nanoparticles were deposited onto TiO₂nanotubes (TNT) in this study to extend their spectral response to the visible region. Gold deposited titanium dioxide nanotubes (AuTNT) were synthesized by using pulse electrodeposition. Electrodeposition was carried out in 0.5 M H₂SO₄ that contained different concentrations (50, 100, 500, and 1,000 µM) of gold solution, with 75% duty cycle and an applied potential of -0.4 V for 20 minutes in a three-electrode electrochemical cell. The TNTs were annealed at 500 °C for 2 hours to induce crystallinity prior to gold deposition. The physicochemical properties of the AuTNT were characterised using a Field Emission Scanning Electron Microscope (FESEM), an Energy Dispersive X-ray (EDX), and an X-ray Diffractometer (XRD). Photoelectrochemical properties of AuTNT electrode was evaluated in 0.5 M Na₂SO₄ and 2 M C₂H₅OH under the illumination of a halogen lamp. The AuTNT electrode prepared with 500 µM gold solution demonstrated the highest photocurrent compared to other concentrations of gold.

Keywords: gold nanoparticles, titanium dioxide nanotube, pulse electrodeposition, photoelectrochemical properties

Abstrak

Pembelahan air secara fotoelektrokimia suria (PEC) untuk menghasilkan hidrogen merupakan teknologi yang bersih, mesra alam, dan kos efektif dengan memanfaatkan cahaya matahari sebagai sumber tenaga. Logam oksida, contohnya TiO₂, lebih digemari sebagai fotoanod dalam pembelahan air PEC kerana logam-logam ini mempunyai kereaktifan yang agak tinggi, stabil dalam larutan akueus, dan lebih murah berbanding semikonduktor bukan oksida. Walau bagaimanapun, TiO₂ mempunyai jurang jalur yang besar (3.2 eV) yang hanya membolehkan ia berfungsi di bawah sinaran cahaya ultralembayung. Oleh itu, nanopartikel emas diendap ke atas nanotiub TiO₂ (TNT) dalam kajian ini untuk mengembangkan tindak balas spektrum TNT ke kawasan cahaya nampak. Nanotiub titanium dioksida yang diendap emas (AuTNT) disintesis menggunakan kaedah nadi elektroendapan. Elektroendapan dilakukan dalam 0.5 M H₂SO₄ yang mengandungi kepekatan (50, 100, 500, dan 1,000 μM) larutan Au yang berbeza dengan 75% kitar tugas dan keupayaan dikenakan pada -0.4 V selama 20 minit menggunakan sel elektrokimia tiga elektrod. Pemanasan nanotiub titanium dioksida telah dilakukan pada suhu 500 °C selama 2 jam untuk meningkatkan struktur kristal TNT sebelum pengendapan emas. Sifat-sifat fizikokimia AuTNT dikaji menggunakan mikroskopi pengimbasan elektron pancaran medan (FESEM), analisis penyerakan tanaga sinar-X (EDX), dan pembelauan sinar-X (XRD). Sifat-sifat fotoelektrokimia AuTNT telah dinilai dalam 0.5 M Na₂SO₄ dan 2 M C₂H₅OH di bawah pencahayaan lampu halogen. Elektrod AuTNT yang disediakan dengan kepekatan larutan Au pada 500 μM memberikan fotoarus yang tertinggi berbanding dengan kepekatan emas yang lain.

Kata kunci: nanopartikel emas, nanotiub titanium dioksida , nadi elektroendapan, sifat fotoelektrokimia

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