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Redalyc.Electrodeposition and Characterization of Palladium Ciência e Natura ISSN: 0100-8307 [email protected] Universidade Federal de Santa Maria Brasil Heydari, Hamid; Abdolmaleki, Abbas; Bagher Gholivand, Mohammad; Shayani-jam, Hassan Electrodeposition and characterization of palladium nanostructures on stainless steel and application as hydrogen sensor Ciência e Natura, vol. 37, núm. 6-1, 2015, pp. 23-33 Universidade Federal de Santa Maria Santa Maria, Brasil Available in: http://www.redalyc.org/articulo.oa?id=467547682005 How to cite Complete issue Scientific Information System More information about this article Network of Scientific Journals from Latin America, the Caribbean, Spain and Portugal Journal's homepage in redalyc.org Non-profit academic project, developed under the open access initiative 23 Ciência e Natura, Santa Maria, v. 37 Part 1 2015, p. 23−33 ISSN impressa: 0100-8307 ISSN on-line: 2179-460X Electrodeposition and characterization of palladium nanostructures on stainless steel and application as hydrogen sensor Hamid Heydari1, Abbas Abdolmaleki2, Mohammad Bagher Gholivand1* and Hassan Shayani-jam3 1 Department of Analytical Chemistry, Faculty of Chemistry, Razi University, Kermanshah 2 Department of Chemistry, Malek Ashtar University of Technology, Tehran 3 Department of Chemistry, Faculty of Science, University of Zanjan, Zanjan E-Mail: [email protected] Abstract Palladium nanostructures have been deposited onto the stainless steel electrode by simple electrochemical deposition method in a buffer solution. The morphology of the synthesized Pd nanoparticles is controllable by deposition potentials because the driving force for various crystal growth mechanisms is merely dependent on applied potentials. The deposited Pd nanoparticles at higher applied potentials showed a cauliflower-like morphology with a nanoscale structure and large surface area. Then, an amperometric hydrogen sensor based on Pd nanoparticles can be constructed. This sensor is based on polymer electrolyte membrane fuel cell (PEMFC) and can be used at the ambient temperature. It is operated in the three-electrode mode that consists of three electrodes (working, counter and reference) and protonated Nafion membrane as proton conducting solid polymer electrolyte (SPE). The steady-state current response is obtained linearly to the concentrations of hydrogen from 50 to 2000 ppm, when a fixed potential of 0.2V is applied to the sensor. Typical factors that influence the performance of the sensor are analyzed and discussed. The simple and inexpensive hydrogen sensor fabricated shows low LOD (10 ppm, based on S/N = 3), wide linear range (50-2000 ppm) and short response time (10-40 s). Keywords: Electrodeposition, Palladium nanostructures, Cauliflower-like morphology, Amperometric hydrogen sensor, Stainless steel. Recebido: dia/mês/ano Aceito: dia/mês/ano 24 ligands or templates, solution-phase synthesis, 1 Introduction chemical vapor deposition, chemical liquid deposition [25], microwave method [26], n recent years, nanoparticles of noble hydrogen reduction and electrochemical metals have been the subject of numerous deposition [27–31]. I research investigations because of their Electrochemical deposition is superior to potential applications as advanced materials other methods morphology controlled synthesis with extraordinary physical and chemical because of the minimum requirement of the properties [1-5]. additives and absence of any interfering and by- The shape-controlled synthesis of metal products generated during the electrodeposition nanoparticles has attracted significant interest of metal nanoparticles. Moreover, the because their properties and applications are nanoparticles can be synthesized in room affected greatly by their morphologies [6-10]. temperature by electrodeposition. Hence, Noble-metal nanoparticles are of special interest electrochemical deposition is a versatile for many applications, including catalysis [11-13] technique that can be used to synthesize sensors [14] and other applications [13, 15]. desirable nanostructures for diverse applications Hydrogen, H2, is one of the most important [10, 31-33]. Under certain conditions, the industrial chemicals and is used in many morphology of electrodeposited metal chemical processes and various industries [16- nanoparticles can be controlled by regulating 19]. In power plants, hydrogen is used for deposition potentials. removing friction heat in turbines. It has also Herein, we report a low cost and simple received much consideration recently in the method for the synthesis of Pd nanostructures search for renewable energy sources, particularly with controllable morphology by electrochemical related to the development of fuel cells based on deposition. Also, this paper explains the hydrogen fuel [20]. Hydrogen is found wide configuration and fabrication of a new application as a fuel in rockets and as a lifting amperometric sensor of hydrogen. It uses a gas in weather balloons. Hydrogen as a fuel in Nafion-117 membrane as a solid phase futuristic automobiles using a H2/O2 fuel cell is a electrolyte and a polytetrafluoroethylene (PTFE) definite possibility, but there is a need for a sheet as a gas-permeable diffusion membrane. hydrogen fuel leak-detection system [21]. This sensor was based on a three-electrode Hydrogen is colorless, odorless, tasteless, electrochemical cell system, employing flammable and explosive, so most human senses palladium nanoparticles deposited on the will not help to detect a leak. For these and other stainless steel as a catalyst for the purpose of reasons, Hydrogen must be monitored. modification of electrodes. Two electrodes with Therefore, substantial efforts are carried out to large surface area are used as a working and a develop sensitive, reliable and inexpensive counter electrode. Another electrode (Pt/air) is hydrogen sensors for the fast detection of used as a reference electrode. The fundamental hydrogen leaks [22-26] principle, construction details and performance Among the various noble metals of the hydrogen sensor is discussed. nanoparticles, Pd nanoparticles has significant performance in the field of hydrogen storage and sensing [27-30]. Also, a simple method for 2 Experimental synthesizing nanostructured Pd with controllable morphology remains a challenge. Up to now, various methods have been 2.1- Electrochemical study and developed to obtain the morphology controlled deposition synthesis of Pd nanoparticles. Most of these All electrochemical measurements were methods are based on the solvothermal and performed at room temperature in a three- hydrothermal processes, the use of surfactants, Recebido: dia/mês/ano Aceito: dia/mês/ano 25 electrode configuration cell, with an Ag/AgCl as of the current became more than 95% of the the reference electrode. An Autolab (model initial current. At the end of electrolysis, the PGSTAT302N) potentiostat/galvanostat was prepared electrode was taken out of the solution used to control the potential applied to the and rinsed with distilled water several times and working electrode. The working electrode used then dried. in the voltammetry experiments and The sensor was prepared according to the electrodeposition was a stainless steel mounted following method. (i) The palladium deposited in Teflon with a specific area exposed to the on stainless steel mesh (working electrode) was solution. The potential of working electrode was placed onto the PTFE membrane. (ii) The Nafion- measured against an Ag/AgCl reference 117 membrane was placed onto working electrode and a platinum wire was used as the electrode and the other side of the membrane counter electrode. was coated with a stainless steel mesh (counter All chemicals were reagent grade and were electrode), a platinum (reference electrode) and used without further purification. an insulator of immediately. (iii) The assembly was placed in a hot-press at 110 °C and kept for 2 2.2- Characterizations 10 min under the pressure of 40 kg/cm [34]. The phase characterization of Pd nanoparticles was performed by means of X-ray diffraction (XRD) using a broker d8 advance X- ray diffractometer with Cu Kα radiation. The morphology and crystalline size of the synthesized Pd samples were determined by using a Field emission scanning electron microscopy (Hitachi S4160 microscope). 2.3- Materials preparation and sensor assembly The schematic diagram of the assembled Figure 1: Schematic diagram of the hydrogen sensor of hydrogen is shown in Figure 1. sensor structure. (1) PTFE membrane, (2) Commercial Nafion membrane from Dupont, working electrode, (3) Nafion-117 membrane, USA (Nafion117) was used as proton conducting (4) counter electrode, (5) reference electrode, (6) solid polymer electrolyte. The membrane was insulator (plexiglas). boiled in 5% H2O2 for 1 h to remove organic impurities. After washing, the membrane was put in one molar Sulfuric acid at 100 °C for 2h to 2.4- Sensor test remove inorganic impurities. After again washing with distilled water, the membrane was Sensor testing was performed at ambient stored in distilled water. pressure and room temperature (25±2 °C). High Stainless steel mesh was used as the working purity dry hydrogen and hydrogen-nitrogen gas electrodes on which the nanostructured Pd was mixtures were used for the measurements. The deposited. Before electrochemical deposition, gas mixtures containing known concentration of Stainless steel mesh was chemically cleaned with hydrogen (in nitrogen) were passed to the acetone using an ultrasonic agitator, followed by sensing-electrode
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