Significant improvement in the hydrogen storage capacity of a reduced graphene oxide/TiO 2 nanocomposite by chemical bonding of Ti–O–C Zahra Gohari Bajestani, Alp Yürüm, Yuda Yürüm To cite this version: Zahra Gohari Bajestani, Alp Yürüm, Yuda Yürüm. Significant improvement in the hydrogen storage capacity of a reduced graphene oxide/TiO 2 nanocomposite by chemical bonding of Ti–O–C. RSC Advances, Royal Society of Chemistry, 2016, 6 (39), pp.32831-32838. 10.1039/c6ra00944a. hal- 02273555 HAL Id: hal-02273555 https://hal.archives-ouvertes.fr/hal-02273555 Submitted on 29 Aug 2019 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. RSC Advances View Article Online PAPER View Journal | View Issue Significant improvement in the hydrogen storage capacity of a reduced graphene oxide/TiO2 Cite this: RSC Adv.,2016,6,32831 nanocomposite by chemical bonding of Ti–O–C† a b a Zahra Gohari Bajestani, Alp Yur¨ um¨ and Yuda Yur¨ um¨ * A series of graphene-based nanocomposites with different TiO2 contents have been prepared via afacile chemical method. All nanocomposites were employed as hydrogen gas adsorption materials at room temperature and pressures up to 10 bar. The effect of dispersion state and size of the particles on the Received 12th January 2016 hydrogen storage capacity of nanocomposites was studied. The highest hydrogen uptake of 0.39 wt% was Accepted 25th March 2016 obtained among prepared nanocomposites and it is 125% higher than the hydrogen adsorption of the DOI: 10.1039/c6ra00944a parent graphene material. This improvement can account for the presence of a high number of active www.rsc.org/advances sites needed for hydrogen molecules and the strong interaction between nanoparticles and graphene sheets. 1. Introduction have been proposed to enhance gas adsorption property of graphene based materials.8,13 So far many theoretical and In recent years, production, storage, and consumption of energy experimental studies have been devoted to functionalization of 2,10,14,15 16–18 have become a serious global problem. Hydrogen attracts graphene by metals and metal oxides in which metal considerable attention in the energy area since it can be a clean oxides offer a great scope for tailor-made carbonaceous adsor- energy resource for the next-generation energy carriers in bents. Due to various advantages e.g., suppressing the re- mobile and stationary power systems.1 However, nding mate- stacking of graphene layers, good bonding and interfacial rials for efficient hydrogen storage is one of the most important interactions with oxygen-containing groups on graphene issues in future of renewable energies.2,3 Several candidates sheets, fabrication of graphene/metal oxide is expected to be an were studied during the last decades as safe and effective effective and practical method toward increasing the hydrogen 13,17 hydrogen adsorbents but none of them met the storage targets storage capacity of graphene. 4–6 set by the U.S. Department of Energy (DOE). Among these TiO2 has been widely studied due to its photochemical, options, graphene a single atomic layer sheet of sp2 bonded catalytic and dielectric characteristics. Theoretical studies Published on 29 March 2016. Downloaded by UNIVERSITE DU MAINE-SCD 8/29/2019 9:12:04 AM. carbon atoms, has been cited as a promising candidate for showed the potential of Ti/TiO2-anchored carbonaceous mate- 17,19,20 energy conversion and storage applications due to its high rials as a hydrogen storage material for room-temperature theoretically surface area, large microporosity, and good applications. Recent experimental results on TiO2-decorated 7–10 21 chemical stability. Nevertheless, the range of reported expanded graphite and TiO2-carbon nanotubes (CNT) 22,23 hydrogen uptakes of graphene at ambient conditions is low.11 composites revealed the enhanced electrochemical 12 4 Srinivas et al. and Huang et al. reached hydrogen uptake of hydrogen uptake of graphene and higher H2 gas adsorption of 0.1 wt% at 10 bar and 0.067 wt% at 57 bar, respectively. Ther- CNT a er impregnation with TiO2 nanoparticles. modynamically, hydrogen molecules are incapable of pene- In this work, TiO2-integrated graphene nanocomposites with ff trating between the graphene layers in graphitic structure di erent amounts of TiO2 nanoparticles were prepared via whereby H2 adsorption generally restricts to the outermost a facile chemical method. We focused on the hydrogen sheets. Weak binding energy between carbon nanostructure adsorption behavior of these nanocomposites at room temper- and H2 at ambient conditions is also another key factor that ature and low pressures that are relevant for practical on-board 8 ff leads to low H2 adsorption capacity of this material. Thus, storage systems. E ects of the loading, dispersion state and size surface modications, such as doping and functionalization of nanoparticles on hydrogen storage capacity of nano- composites were studied. Homogenous dispersion of TiO2 nanoparticles with diameter of <20 nm was found to enhance aFaculty of Engineering and Natural Sciences, Sabanci University, Tuzla, Istanbul, the hydrogen storage capacity of parent graphene by 125%. 34956, Turkey. E-mail: [email protected] Higher hydrogen uptake of nanocomposites compared to that bSabanci University Nanotechnology Research and Application Center, Tuzla, Istanbul, of graphene sample was related to strong attachment of highly 34956, Turkey † Electronic supplementary information (ESI) available. See DOI: distributed nanoparticles to the underlying graphene sheets. 10.1039/c6ra00944a This journal is © The Royal Society of Chemistry 2016 RSC Adv.,2016,6, 32831–32838 | 32831 View Article Online RSC Advances Paper 2. Experimental section electron microscopy (SEM) images were taken by Jeol 2000FX with the accelerating voltage of 200 kV and Leo Supra 35VP eld 2.1 Materials emission scanning electron microscope with an acceleration – – Natural graphite ake (99%), sulfuric acid (H2SO4, 98%), voltage of 2 kV, respectively. The Brunauer Emmett Teller sodium nitrate (NaNO3), potassium permanganate (KMnO4) (BET) speci c surface area and porosity of samples were deter- and hydrochloric acid (HCl, 37%) were purchased from Sigma- mined by analyzing the standard nitrogen adsorption isotherms Aldrich. Hydrogen peroxide (H2O2, 30%) and titanium chloride at 77 K using nova 2200e, Quantachrome instruments. (TiCl3) were obtained from Merck. All reagents were analytical Hydrogen storage capacity of samples was measured by using grade and used without further purication. Intelligent Gravimetric Analyzer (IGA 001, Hiden Isochema). All nanocomposites (20–25 mg) were degassed at 100 C for 12 h À 2.2 Preparation under high vacuum (10 7 mbar) prior to measurements and then, hydrogen adsorption isotherms were measured at 298 K Graphite oxide was prepared from natural graphite akes using 24 up to 10 bar. Hummers' method. In order to prepare TiO2-integrated gra- phene sheets, hereaer referred to as RGO–T nanocomposites, graphite oxide was rst sonicated (Vibra Cell 75041, Bioblock 3. Results and discussion Scienti c) in water for 2 h to obtain a homogenous dispersion of 3.1 Materials characterization graphene oxide (GO) in aqueous medium. Different amounts of X-ray diffraction was rst carried out to determine the crystal- TiCl3 were then added to the mixture to reach Ti loading of 3 wt%, 5 wt%, and 7 wt%. Aer stirring for 24 h, suspensions were lographic structure of the samples. As shown in Fig. 1a, natural ltered, vacuum-dried at 60 C and reduced at 1000 C for 12 min under argon atmosphere to obtain reduced graphene oxide (RGO) with different amounts of TiO2, named as RGO–T3, RGO– T5, and RGO–T7 in accordance with increasing amount of TiCl3 in the mixing step. Thermogravimetric analysis indicated the – presence of 10 wt%, 12 wt% and 15 wt% TiO2 in RGO T3, RGO–T5, and RGO–T7, respectively (Fig. S1, ESI†). As a refer- ence, GO (without addition of TiCl3) was thermally reduced at 1000 C to attain fully exfoliated reduced graphene oxide. 2.3 Characterization X-Ray diffraction (XRD) patterns were performed using Bruker AXS diffractometer tted with a Siemens X-ray gun using 0.15406 nm Cu Ka radiation. Raman spectroscopic analysis was carried out using Renishaw inVia reex Raman spectrometer – À1 Published on 29 March 2016. Downloaded by UNIVERSITE DU MAINE-SCD 8/29/2019 9:12:04 AM. with a 532 nm laser beam in the range of 100 3500 cm while samples were loaded on silicon wafer and focused with a 50Â objectives. X-ray photoelectron spectroscopy (XPS) analyses were conducted on a Thermo K-alpha X-ray photoelectron – a Fig. 2 Raman spectra of graphite oxide, RGO and RGO T nano- spectrometer with a monochromated Al K supported by a low composites, from bottom to top: graphite oxide, RGO, RGO–T3, energy electron/ion ood gun for charge neutralization. Trans- RGO–T5 and RGO–T7. Inset magnifies the wavenumber of 100–900 mission electron microscopy (TEM) micrographs and scanning cmÀ1 in RGO–T7. Fig. 1 XRD patterns of (a) GO and (b) RGO samples with increasing amount of Ti addition.