Higher water splitting hydrogen generation rate for single crystalline anatase phase of TiO₂ nanotube arrays

School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Seberang Perai Selatan, Pulau Pinang, Malaysia

^a e-mail: srimala@eng.usm.my

Received: 25 June 2012
Revised: 2 August 2012
Accepted: 3 August 2012
Published online: 3 September 2012

Abstract

This paper presents a detailed investigation on the effect of heat-treatment process on the highly ordered titanium dioxide (TiO₂) nanotube arrays in connection with the photoelectrochemical (PEC) response and hydrogen evolution rate. TiO₂ nanotube arrays have been systematically heat-treated to control the transformation of as-anodized TiO₂ amorphous structure to crystalline anatase and rutile phases. In this study, single crystalline TiO₂ anatase phase exhibited a higher PEC response and hydrogen evolution rate at 400 °C heat treatment. The photocurrent density increase was mainly attributed to the effective transport of photo-induced electrons within the single crystal anatase phase. However, polycrystalline anatase and rutile phases showed the fluctuation in lower photocurrent density upon heat treatment above 500 °C. The mobility of photo-induced electrons was obviously hindered due to the recombination losses in defect sites between the anatase and rutile phase.