Applied Surface Science 319 (2014) 205–210 Contents lists available at ScienceDirect Applied Surface Science jou rn al h om ep age: www.elsevier.com/locate/apsusc Enhanced solar water splitting of electron beam irradiated titania photoanode by electrostatic spray deposition Mukund G. Mali a,1 , Hyun Yoon a,1 , Seongpil An a , Jae-Young Choi a , Ha-Yong Kim a , Byung Cheol Lee b , Byung Nam Kim b , Ji Hyun Park b , Salem S. Al-Deyab c , Sam S. Yoon a,∗ a School of Mechanical Engineering, Korea University, Seoul 136-713, Republic of Korea b Radiation Equipment Research Div., Korea Atomic Energy Res. Inst., Daejeon 305-353, Republic of Korea c Department of Chemistry, College of Science, King Saud University, Riyadh 11451, Saudi Arabia a r t i c l e i n f o Article history: Received 25 April 2014 Received in revised form 10 June 2014 Accepted 13 June 2014 Available online 20 June 2014 Keywords: Electrostatic spray deposition Water splitting Electron beam TiO2 Thin film a b s t r a c t Surface modifications are often made to titania films to improve its photocatalytic performance in water splitting. We herein introduced electron beam irradiation to enhance the photocatalytic activities of an electro-sprayed titania film for solar water splitting application. The film was fabricated by a facile and scalable electrostatic spraying deposition. According to SEM, X-ray diffraction, and Raman data, electron beam densified the film and improved its crystallinity. Absorbance data indicated that the band gap of the E-beam film reduced, which in turn covered the wider range of absorbed light. These modifications increased oxygen vacancies or defects, which enhanced mobility and separation of electrons and holes. As a result, the E-beam film exhibited a threefold increase in the photocurrent density, compared to that of the non-E-beam film. This electrosprayed titania film was used as a photoanode while the reference and counter electrodes involved in the generation of hydrogen were made of Ag/AgCl and platinum, respectively. The intensity of the UV light illumination used was 1 mW/cm 2 . © 2014 Elsevier B.V. All rights reserved. 1. Introduction Photoelectrochemical (PEC) cells are capable of harvesting the highly abundant supply of sunlight to produce energy in the form of chemical energy stored within hydrogen, which is produced by water splitting. To trigger photocatalysis, semiconducting materi- als are needed that can absorb a level of energy equal to or higher than the material’s band gap when exposed to photon energy. When this occurs, excited electrons (e - ) migrate to the conduc- tion band, thus leaving behind holes (h + ) in the valence band of the semiconductor photoelectrode. Ultimately, these excited electrons travel to the cathode, where they undergo a reduction process, whereas the holes combine with water and produce oxygen at the anode. To achieve higher PEC performance, the top of the valence band (VB) should secure a higher potential than that of oxidation of H 2 O/O 2 (1.23 vs NHE). Similarly, the bottom of the conduction band should secure a lower potential than that of reduction of H + /H 2 (0 vs NHE) [1]. The performance of any PEC cell is therefore completely dependent upon the nature of the semiconductor material used ∗ Corresponding author. Tel.: +82 2 3290 3376; fax: +82 2 926 9290. E-mail address: skyoon@korea.ac.kr (S.S. Yoon). 1 These authors contributed equally to this work. as the photoelectrode. However, the quantum efficiency of this semiconductor is adversely affected by the recombination of holes and electrons. Consequently, in order to achieve better PEC water- splitting performance, the semiconductor photoelectrode should be modified in such a way that it restricts the recombination of electrons and holes. Titania (TiO 2 ) has long been considered one of the most pop- ular semiconducting materials for use in PEC water splitting, due largely to the pioneering work by Fujishima and Honda in 1972 [2]. Since then, titania has been widely accepted for its high physical and chemical stability, greater oxidizing capacity, nontoxic nature, and low price. Furthermore, the band gap energy of titania is suit- able for the oxidation and reduction of water, with just a slight modification of the defect chemistry and oxygen stoichiometry all that is required to tune its electronic properties. Park et al. have previously reported an improved absorption of visible light (>420 nm) after doping of carbon onto TiO 2 nanotube arrays [3]. Similarly, Zhang et al. modified sol–gel synthesized TiO 2 by nitrogen doping in order to improve its photocatalytic activ- ity [4]. Adopting a slightly different approach, Maijenburg et al. successfully synthesized Ag/TiO 2 nanowires to achieve improved water splitting over empty TiO 2 nanotubes [5]. Kumar et al. reported the modification of the work function and surface poten- tial of TiO 2 thin films by exposing them to dense electron excitation http://dx.doi.org/10.1016/j.apsusc.2014.06.097 0169-4332/© 2014 Elsevier B.V. All rights reserved.