Photoelectrocatalytic degradation of organic pollutants via a CdS quantum dots enhanced TiO2nanotube array electrode under visible light irradiation

Abstract

Ultra-fine CdS quantum dots modified TiO₂ nanotube arrays (TiO₂-NTs) with enhanced visible-light activity are fabricated via a cathodic electro-deposition combined with ion-exchange route (CEDIE). The as-formed CdS quantum dots were highly dispersed both outside and inside the TiO₂-NTs. The proposed CEDIE strategy results in the strong combination and heterojunctions between CdS and TiO₂ through Cd–O bonds. The crystal phases, chemical compositions and physicochemical properties of as-obtained CdS/TiO₂-NTs have been investigated based on various characterizations. Compared to CdS/TiO₂-NTs prepared via a sequential chemical bath deposition method, the as-synthesized samples exhibit stronger visible-light absorption capability, higher photocurrent density, excellent stability, and greatly enhanced photoelectrocatalytic (PEC) activity toward degradation of methyl orange (MO) aqueous solutions under visible light irradiation (λ > 400 nm). Such enhanced PEC activity may be ascribed to the strong combination and heterojunctions between CdS and TiO₂, favorable for visible-light response and charge separation of TiO₂-NTs.