Enhanced visible-light-induced photoelectrocatalytic degradation of methyl orange by CdS sensitized TiO₂ nanotube arrays electrode

In this work, CdS sensitized TiO₂ nanotube arrays (CdS/TiO ₂NTs) electrode was synthesized with the CdS deposition on the highly ordered titanium dioxide nanotube arrays (TiO₂NTs) by sequential chemical bath deposition method (S-CBD). The as-prepared CdS/TiO₂NTs was characterized by field-emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). The results indicated that the CdS nanoparticles were effectively deposited on the surface of TiO₂NTs. The amperometric I-t curve on the CdS/TiO₂NTs electrode was also presented. It was found that the photocurrent density was enhanced significantly from 0.5 to 1.85 mA/cm² upon illumination with applied potential of 0.5 V at the central wavelength of 253.7 nm. The photoelectrocatalytic (PEC) activity of the CdS/TiO₂NTs electrode was investigated by degradation of methyl orange (MO) in aqueous solution. Compared with TiO₂NTs electrode, the degradation efficiencies of CdS/TiO₂NTs electrode increased from 78% to 99.2% under UV light in 2 h, and from 14% to 99.2% under visible light in 3 h, which was caused by effective separation of the electrons and holes due to the effect of CdS, hence inhibiting the recombination of electron/hole pairs of TiO₂NTs.