Materials Chemistry and Physics 128 (2011) 507–513 Contents lists available at ScienceDirect Materials Chemistry and Physics journal homepage: www.elsevier.com/locate/matchemphys Poly phenylenediamine and its TiO 2 composite as hydrogen storage material Mona H. Abdel Rehim a , Nahla Ismail b,∗ , Abd El-Rahman A.A. Badawy b , Gamal Turky c a Packing and Packaging Materials Department, Center of Excellence for Advanced Science, Renewable Energy Group, National Research Center, Cairo, Egypt b Physical Chemistry Department, National Research Center, Center of Excellence for Advanced Science, Renewable Energy Group, National Research Center, El-bohooth St 33, Cairo, Egypt c Microwave Physics and Dielectrics Department, National Research Center, Cairo, Egypt article info Article history: Received 29 September 2010 Received in revised form 18 January 2011 Accepted 21 March 2011 Keywords: Polypheneline diamine Hydrogen storage Polymer composite abstract Poly phenylenediamine was synthesized from 1,4-phenylenediamine in presence of potassium persul- phate and salicylic acid. The structure of the formed poly phenylenediamine was traced using FTIR and its morphology was examined by transmittance electron microscope (TEM). Gel permeation chromatogra- phy (GPC) was used to evaluate the polymer molecular weight which showed that the value of its molar mass is 20,000 g mol -1 and it has polydispersity index of 1.01. Different concentrations of TiO 2 were incorporated in the poly phenylenediamine structure via coordination bond between the oxygen atom of TiO 2 and the hydrogen atom of N–H group of polymer. The prepared composites were characterized using FTIR, TA, TEM and SEM/EDX. The TEM micrographs revealed that the composites have 2-D network structure and its morphology changed from a dendritic structure for the pure polymer to layered struc- ture of the composite. The polymer and its composite are completely insulators. Their hydrogen storage capacity has been estimated at -193 ◦ C and the composite reported higher hydrogen uptake values than the pure polymer. The reason is suggested to be due to the layered structure of composite which gives it the privilege to store more hydrogen in its interlayer vicinity. © 2011 Elsevier B.V. All rights reserved. 1. Introduction With the accelerating demand for cleaner and more efficient energy sources, hydrogen research has attracted more attention in the scientific community. Hydrogen is an ideal fuel; it is abundant, renewable and its combustion produces only water vapor and heat. Until now, full implementation of a hydrogen-based energy system has been hindered in part by the challenge of storing hydrogen gas. There are different storage systems proposed by scientists. Gaseous and liquid hydrogen tanks, gaseous storage tank suffers a major drawback of small amounts of hydrogen stored in required volume, while liquefied hydrogen suffers a major obstacle of severe require- ments of liquefaction [1,2]. On the other hand, researchers have given attention to solid-state hydrogen storage, metal hydrides and complex metal hydrides have been studied in the last four decades so that atomic hydrogen is stored in the interstitial sites and by des- orption hydrogen recombines on the material surface and released as molecular hydrogen. Thousands of elements, compounds and alloys are listed as metal hydrides but no material yet meets all the requirements of targeted storage system [3,4]. A wide vari- ety of approaches including carbon nanostructures [5] graphite and ∗ Corresponding author. E-mail address: nahlaismail24@yohoo.com (N. Ismail). activated carbon [6], metal/carbon nanostructures [7], carbon aero- gels [8], metal–organic frameworks [9,10], few have been published about the use of synthetic polymers in this application. Conductive polymers such as polyaniline and polypyrrole have been studied as hydrogen storing materials and it was found that after treatment with HCl, the polymers showed high hydrogen sorption up to 8 wt% at room temperature and under 9.3 MPa [11]. It was suggested that both the molecular effect and electrical effects appear to play an important role in hydrogen sorption. Phenylenediamine (PDA) isomers are aniline derivatives that also yield polymers upon oxidation. Their structure has not been elucidated, but in principle all three isomers could produce, in addi- tion to poly aniline (PAni) -like chains, phenazine units [12,13]. Poly 1,4-phenylenediamine (PPDA) has been studied alone [14] and in the copolymerization of aniline with phenylenediamine [13,15]. PPDA has demonstrated a great potential for use as electrochromic display materials, humidity sensors, electrode-modified materials, pH response, and protection against metal corrosion [13,16]. The dielectric properties of the PPDA and its composite have been evaluated. Among spectroscopic methods for polymers and their composites, broadband dielectric spectroscopy, BDS, has the wide range of frequency 10 -6 to 10 12 as a unique characteristic. Over this range of frequency the polymer respond to applied elec- tric field is the key feature that enables one to relate the dielectric response to slow and/or fast molecular events at low and high fre- quencies, respectively. A strong industrial interest in dielectric and 0254-0584/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.matchemphys.2011.03.037