Electrodeposited Cobalt Alloys as Materials for Energy Technology
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Electrodeposited Cobalt Alloys as Materials for Energy Technology Maryna Glushkova1, Tetiana Bairachna2, Maryna Ved1 and Mykola Sakhnenko1 1 Department of Inorganic Substances Technology, National Technical University “Kharkiv Polytechnic Institute”, 21 Frunze St, Kharkiv, UA 61002, Ukraine 2 Department of Chemistry and Chemical Biology, Northeastern University, 360 Huntington Ave., Boston, MA 02115, U.S.A. ABSTRACT The influence of electrodeposition parameters on chemical composition, morphology and functional properties of such binary cobalt alloys as CoAg, CoW, and CoFe has been investigated. The alloys are shown to possess catalytic properties. Catalytic activity was preliminary estimated in the electrolytic hydrogen evolution reaction and tested by CO to CO2 conversion during the catalytic benzene oxidation. INTRODUCTION Metallic platinum and its alloys are known to be the most effective materials as catalysts, but their significantly high cost limits their usage. The focus of this study was to synthesize a replacement for the platinum based catalysts. Cobalt alloys were taken into consideration since they are highly effective in heterogeneous redox reactions [1-6]. The goal was to establish a relationship between the chemical composition and surface morphology and functional properties of binary cobalt alloys, namely CoAg, CoW, and CoFe. EXPERIMENTAL CoFe and CoW alloys were deposited from citrate electrolytes and CoAg - from citratepyrophosphate. Electrodeposition was conducted in a standard three electrode glass cell at room temperature using a IPCPro M potentiostat in the pulse for CoAg and CoW and galvanostatic for CoFe mode. A platinum mesh was used as a counter electrode, and a saturated calomel electrode (SCE) was utilized as a reference electrode. The pH value was corrected by sodium hydroxide and boric acid and controlled by a pH-meter 150M. Thin films alloys were deposited onto copper, nichrome and steel substrates, respectively. The pre-experimental substrate preparation consisted of degreasing, washing and etching in the mixture of nitric and sulfuric acids (for copper and steel) and a saturated solution of ferric chloride (III) at 333 K (for nichrome). Weighing was performed before and after deposition to calculate current efficiency through Faraday’s law. Chemical composition of CoW, CoFe and CoAg alloys was determined by X-ray fluorescence analysis using a portable spectrometer “SPRUT”. Surface morphology was examined by scanning electron microscope ZEISS EVO 40XVP. The CoAg and CoW coatings surface roughness was investigated by scanning atomic force microscopy (AFM) NT-206. Electrocatalytic and corrosion properties of CoW alloy thin films were determined from polarization dependencies in the solution of 0.001 M sulfuric acid and 1 M sodium sulfate. The cell was deoxygenated purging high purity argon for 15 min. The CoW alloy thin films were milled in strips of about 10×5 mm for catalytic property in a catalytic benzene oxidation reaction
experiment. The experiment was conducted by varying sp
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