Electroanalytical Sensing of Bromides Using Radiolytically Synthesized Silver Nanoparticle Electrocatalysts

Monitoring bromides (Br-) is of crucial importance since bromates, potential human carcinogens, are formed during ozonation of water containing bromides in concentrations GT 100 mu gL(-1). Within this study, silver (Ag) and four carbon-supported Ag catalysts were synthesized by the gamma-radiation method and their morphology and structure examined using transmission electron microscopy, X-ray diffraction, and UV-Vis analysis. The nanocatalysts were tested for Br- sensing in aqueous media using cyclic voltammetry. All five Ag materials exhibited electroactivity for sensing of Br- ions, with pure Ag catalyst giving the best response to Br- ions presence in terms of the lowest limit of detection. Sensing of bromides was also explored in tap water after addition of bromides suggesting that herein prepared catalysts could be used for bromides detection in real samples. Furthermore, sensing of other halogen ions, namely, chlorides and iodides, was examined, and response due to chloride presence was recorded

Improved Poly(vinyl alcohol) (PVA) based matrix as a potential solid electrolyte for electrochemical energy conversion devices, obtained by gamma irradiation

PVA (Poly(vinyl alcohol)) matrixes were developed for potential application in electrochemical energy conversion devices, like batteries, alkaline fuel cells and electrolyzers. They were prepared by gamma-irradiation of aqueous PVA solutions, followed by different post irradiation treatments. By immersion in an electrolyte they become membranes with high ionic conductivities. The treatments were shown as the key factor determining the conductivity, through affecting their structure. An improved structure has large fractional free volume, and allows high electrolyte uptake and thus high conductivity (0.30 S cm(-1) -0.34 S cm(-1)). The structure, as well as the conductivity, has not been changed even after a period of 14 months, although the membranes have been exposed to strong alkaline medium. Besides high and long-term conductivity of the KOH doped membranes, other important properties for application in the devices were investigated, like thermal stability and gas crossover through the membranes. The 10% PVA(25kGy) membrane doped with saturated LiNO3 solution was tested in a rechargeable aqueous Li-ion battery. Due to its high conductivity it allowed an electrode material to have the same coulombic efficiency as it would have in liquid LiNO3, showing good compatibility with the material. All these properties make the memebranes attractive candidates for possible application in the electrochemical devices. (C) 2015 Elsevier Ltd. All rights reserved

Radiolitically synthesized nano Ag/C catalysts for oxygen reduction and borohydride oxidation reactions in alkaline media, for potential applications in fuel cells

Carbon-supported silver nanoparticles (Ag:NPs/C) were synthesized by gamma irradiation-induced reduction method using the poly(vinyl alcohol) or poly(vinyl alcohol)/chitosan polymer as stabilizer. Prepared samples were characterized using transmission electron microscopy and X-ray diffractometry. Subsequently, Ag:NPs/C were studied using rotating disc and rotating ring disc method as electrocatalysts for ORR (oxygen reduction reaction) and BOR (borohydride oxidation reaction) for potential application in alkaline fuel cells. The synthesis method used herein offers simple and fast approach for catalytic ink preparation, since the ink is prepared in one-step radiation process, simultaneously with Ag+ ions reduction. Very high and stable catalytic efficiency toward ORR via 4e(-) path was evidenced during 4000 square pulse polarization cycles. BOR, accompanied with the simultaneous borohydride ion hydrolysis, was found to proceed at the oxidized Ag surface. (C) 2016 Elsevier Ltd. All rights reserved