The most promising pathway to convert solar energy into H2(g) is the photocatalytical splitting of water. In this context, TiO2 has been reputed as an adequate material [1]. Nevertheless, the visible light harvesting ability of TiO2 has been considered a key issue, once a significant fraction of incident solar energy is in the visible region. The sensitization of TiO2 with low-energy semiconductors, such as CdSe (Eg = 1.7 eV), has been studied as a simple tool to adjust this limitation [2]. The aligned 1D nanostructure, such as nanotube, have been highly employed to provide a direct pathway for charge transport as well as high optical absorption cross-section. In light of this, the present work describes the pulsed electrodeposition of CdSe intro/onto TiO2 nanotubes (TiO2NT) obtained at two different potentials (20 and 40 V) and, pre- and post- annealing. For this, measurements of SEM, XRD (with Rietveld refinement), Mott-Schottky, and photocurrent were carried out. The TiO2NT’s were anodically obtained as described by R.G. Freitas et al. [1]. The electrodeposition of CdSe intro/onto TiO2NT’s was performed by pulsed electrodeposition method and using an electrolytic bath containing 5 mM Cd2+, 1 mM SeO2, and 0.5 M H2SO4. The deposition was carried out during 1000 s; the potentials of -0.76 V and -0.64 V were used in the cathodic and anodic pulse and the duration of each pulse per cycle was of 25 s and 15 s, respectively. The morphology observed by SEM has led us to conclude that the CdSe was deposited into and onto the TiO2NT’s. From Rietveld refinements of the XRD patterns, it was noted an insertion of Cd and Se atoms in the TiO2 array when the CdSe was deposited before annealing. This insertion was also observed from Mott-Schottky characterization, these last films had 10 to 100 times more donor densities than the films where the CdSe was deposited after annealing (CSafterTiO2NT films). The most prominent impact was observed in the photocatalytical properties; the photocurrent intensity associated to water splitting for the CSafterTiO2NT films was almost 2 times higher than the observed for other ones. Thus, it was possible to obtain using an electrochemical route CdSe/TiO2NT films and we could conclude that more efficient water splitting was achieved when CdSe is deposited intro/onto annealed TiO2. [1] R.G. Freitas et al. Electrochim. Acta. 136 (2014) 404–411 / J. Power Sources 251 (2014) 178–186. [2] H. Sik Kim et al. Mater. Lett. 111 (2013) 47–50.

Electrochemical fabrication of CdSe/TiO2 nanotubes for photoelectrocatalytical water splitting application

249th National Meeting (2015)

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