The electrocatalytic activity of several materials for the nitrate reduction reaction was studied by cyclic voltammetry on a rotating ring disc electrode in solutions with different concentrations of sodium bicarbonate. Copper exhibited highest catalytic activity among the materials studied. Nitrate reduction on copper was characterized by two cathodic shoulders on the polarization curve in the potential region of the commencement of hydrogen evolution. In this potential range an anodic current response was observed on the Pt ring electrode identified as nitrite to nitrate oxidation. This indicates that nitrite is an intermediate product during nitrate reduction. These conclusions were verified by batch electrolysis using a plate electrode electrochemical cell. Copper and nickel, materials representing the opposite ends of the electrocatalytic activity spectra, were used in batch electrolysis testing.
"the formation of nitrite and ammonia  . Vorlop and Tacke  were the first to report that a second metal, Pd, in addition to Cu could improve the N 2 selectivity during the electrochemical reduction of nitrate. "
[Show abstract][Hide abstract] ABSTRACT: Cu and Pd–Cu (Pd = 40 wt%) electrodes supported on stainless steel (Cu/SS and Pd–Cu/SS) were prepared using electrodeposition methods and characterized by X-ray diffraction, scanning electron microscope, and X-ray photoelectron spectroscopy. The electrocatalytic reduction of nitrate on Cu/SS and Pd–Cu/SS electrodes was studied in sodium perchlorate electrolyte. By tuning the applied potential, nitrate was found to be selectively reduced to different products, indicating a strong dependence of nitrate reduction reaction on the applied potential. Moreover, the effect of electrode material on nitrate reduction was studied also. Results showed that the nitrate reduction over the two electrodes was different due in part to distinct surface morphology. Results demonstrated a novel avenue to improve the selectivity of nitrate reduction products through controlling the applied potential and selection of electrode material. Results also showed strategy warrant further studies on nitrate conversion to harmless nitrogen gas.
"Inorganic by-products are also generated (Bergmann and Koparal, 2005; Bergmann et al., 2001; Gordon et al., 1998; Bouzek et al., 2001; White, 1999). Nitrites and ammonia produced by the cathodic reduction of nitrates were found to decrease the current efficiency of hypochlorite formation (Bergmann and Koparal, 2005; Bergmann et al., 2001; Gordon et al., 1998; Bouzek et al., 2001; White, 1999). This paper deals only with current losses occurring during the electrolysis of a dilute pure sodium chloride solution. "
[Show abstract][Hide abstract] ABSTRACT: A mathematical model was set up for anodic, cathodic and overall current efficiencies of an electrochemical cell for hypochlorite production acting as an ideal stirred reactor. A 0.06-0.20 mol dm−3 NaClO hypochlorite solution was obtained in the cell by the electrolysis of 0.25-0.50 mol dm−3 sodium chloride solution at a temperature of 20 °C, at a current density of 100 mA cm−2 and at 8.3 < pH < 8.7. Anodic current losses occur through hypochlorite and water oxidation at the DSA anode, and cathodic current losses result from hypochlorite reduction at the titanium cathode.
Chemical Engineering Research and Design 01/2015; 93:591-601. DOI:10.1016/j.cherd.2014.07.025 · 2.28 Impact Factor
"and Fe . Among these materials, copper is known to be the most efficient electrocatalyst for nitrate electroreduction producing ammonium as a final product   . Thus, electrochemical treatment of nitrates on pure Cu cathodes    or Cu alloys [21,38–40] has been widely studied. "
[Show abstract][Hide abstract] ABSTRACT: The aim of this work was to set up a novel electrochemical system allowing an efficient transformation of concentrated nitrate solutions to ammonium and which can be subsequently implemented on a large scale application. First, this paper describes the preparation of a porous copper modified electrode by successive electrodeposition of nickel then copper on a graphite felt of large specific surface area. Homogeneous Cu coating of all fibres in the 3D porous structure was successfully obtained using low concentrations of copper salts and high applied current intensities. The porous copper electrode was then used in a flow electrochemical process to achieve a selective and quantitative transformation of concentrated nitrate into ammonium. Different electrolytic solutions, slightly acid (acetate buffer) or neutral (phosphate buffer), and flow rates were investigated. The nitrate solution was quantitatively reduced into NH4+ with high selectivity in only one pass through the electrode. When the applied current was similar to the theoretical one, the maximum selectivity (96%) and the best current efficiency (72%) for NH4+ formation were reached at pH 7.2 with a flow rate of 2 mL min-1. The obtained ammonium solution can be subsequently used either as a potential nitrogen source during microbial culture or simply as a fertilizer.
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