Regular Article Enhanced photoelectrochemical performance of TiO 2 nanofiber arrays decorated with CdS nanoparticles via SILAR method Jamila Ben Naceur 1,* , Rachid Ouertani 1 , Fatma Jrad 1 , Saleh Khamlich 2,3 , Wissem Dimassi 1 , and Radhouane Chtourou 1 1 Laboratory of Nanomaterials and Renewable Energy Systems, Research and Technology Center of Energy, Borj-Cedria Science and Technology Park, BP 95, Hammam-Lif 2050, Tunisia 2 UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, PO Box 392, Pretoria, South Africa 3 Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, PO Box 722, Somerset West, Western Cape Province, South Africa Received: 30 July 2020 / Accepted: 7 January 2021 Abstract. In this paper, we report the photoelectrochemical performances of CdS nanoparticles (NPs) decorated TiO 2 photoanodes. The TiO 2 nanofiber arrays (NFAs) were fabricated into Titanium substrate by a hydrothermal method. Afterwards, the deposited TiO 2 NFAs were decorated with CdS NPs by employing a successive ionic layer adsorption and reaction (SILAR) method. The obtained samples of CdS covered and uncovered TiO 2 NFAs were characterized by X-ray diffraction, Scanning Electron Microscopy and UV-visible Diffuse Reflectance Spectroscopy. The size of the CdS nanoparticles increases with the number of SILAR cycles and leads to an additional broad absorption peak in the visible part of the spectrum. Consequently, the photo- electrochemical performance of the CdS decorated TiO 2 was enhanced substantially resulting in a better electron-hole separation and transport. This enhancement has been discussed and assigned to a better sun light harvesting and an efficient charge transfer between the CdS nanoparticles and the TiO 2 NFAs. 1 Introduction Recently, photoactive semiconductor metal oxides have been highly investigated for applications such as photo catalysis and photoelectrochemical water splitting [1–6]. Among numerous oxides, TiO 2 is considered as the most studied candidate due to its non-toxicity, chemical stability and to its high photo-activity properties [7–10]. Nevertheless, the morphology of TiO 2 films plays an important role in the charge transport and collection. TiO 2 nanostructures exhibit better photocatalytic and photo- electrochemical activities than continuous thin films owing to their high surface-area-to-volume ratio. It has been established that this morphological propriety offers an efficient charge separation and carrier mobility inducing a better charge carrier collection efficiency [11–13]. Conse- quently, remarkable investigative efforts have been dedicated to constructing nanostructured 1-D structures. However, the main drawback of the application of TiO 2 oxide semiconductor is related to its large band gap which limits its absorption in the UV region and thus affecting its photocatalytic activity and PEC efficiency [14–16]. Hence, in order to sort out this issue, several groups have considered various approaches such as doping, adsorbing dye sensitizer and adding a narrow band gap semiconduc- tor [17–19]. On our side, we synthesized a hybrid structure where TiO 2 nanofibers were coated with cadmium sulfide (CdS) nanoparticles by using a cost effective approach. Actually, CdS is a kind of p type semiconductor with small band gap, higher carrier mobility, good stability and good light harvesting at the visible region which corresponds to nearly 50% of the entire solar spectrum [20–22]. Further- more, due to its band gap position and tenability, CdS exhibits good contacts and electronic couplings with TiO 2 , allowing easy photo-generated charge transfer [23]. In recent years, photo-electrochemical cells (PECs) and CdS decorated TiO 2 were studied by many researches. For instance, Tang et al., combined hydrothermal and successive ionic layer adsorption and reaction (SILAR) methods to synthesis CdS and Cu 2 S nanoparticles coated TiO 2 branched nanorod arrays on fluorine doped tin oxide (FTO). They used the fabricated CdS/Cu 2 S/TiO 2 hetero- structures as working electrode in photoelectrochemical water splitting system [24]. Again, using FTO as substrates, Jiajia et al., prepared CdS nanoparticles sensitized TiO 2 nanorods arrays (NRAs) using SILAR and hydrothermal methods, respectively. They reported that the CdS/TiO 2 NRAs obtained after 8 SILAR cycles showed, under visible light, better degradation rate of methyl orange (42.96%) and photocurrent density (168.5 mA/cm 2 ) compared to bare TiO 2 NRAs [25]. In addition, Xie et al., have elaborated CdS quantum dots sensitized TiO 2 NRAs onto FTO substrate by * e-mail: jamila2.bennaceur@gmail.com Eur. Phys. J. Appl. Phys. 93, 20302 (2021) © EDP Sciences, 2021 https://doi.org/10.1051/epjap/2021200249 THE EUROPEAN PHYSICAL JOURNAL APPLIED PHYSICS 20302-p1