Sonoelectrochemical synthesis of highly photoelectrochemically active TiO2 nanotubes by incorporating CdS nanoparticles

Self-organized anodic TiO2 nanotube arrays (TiO2NTs) are functionalized with CdS nanoparticle based perfusion and deposition through a single-step sonoelectrodeposition method. Even controlled at 50 degrees C, CdS nanoparticles with smaller size and more homogeneous distribution are successfully synthesized in dimethyl sulfoxide (DMSO) under ultrasonic irradiation. Moreover, TiO2 nanotubes can be filled with nanoparticles because of the ultrasonic effect. The CdS incorporated TiO2NTs (CdS-TiO2NTs) effectively harvest solar light in the UV as well as the visible light (up to 480 nm) region. Compared with pure TiO2NTs, a more than ninefold enhancement in photocurrent response is observed using the CdS-TiO2NTs. Maximum incident photon to charge carrier efficiency (IPCE) values of 99.95% and 9.85% are observed respectively for CdS-TiO2 nanotubes and pure TiO2NTs. The high value of IPCE observed with the CdS-TiO2NTs is attributed to the increased efficiency of charge separation and transport of electrons. A schematic diagram is proposed to illustrate the possible process of CdS formation in nanotubes under sonochemical and electrochemical conditions.