DEMS-monitoring liquid | gas interfacial ammonia oxidation at carbon nanofibre membranes

Abstract

Electrochemical ammonia oxidation is of interest in waste treatment as well as in electrochemical sensing applications and demonstrated here at a carbon nanofibre (''bucky-paper'') electrode. The electrode is placed at the aqueous electrolyte | gas interface, and current (cyclic voltammetry) as well as ambient differential electrochemical mass spectrometry (DEMS, cyclic voltbarometry) data are recorded as a function of solution composition and pH. The oxidation of oxalate to CO 2 is employed as a test and calibration system. Anodic polarization of the carbon nanofibre membrane in inert aqueous electrolyte is shown to result in direct sustained anodic CO 2 evolution. In alkaline aqueous media (starting at pH 9) significant levels of nitrogen from ammonia are produced in competition to CO 2 formation from carbon nanofibres without the need for additional catalysts. However, for applications with low level ammonia, catalysts will be required to minimize current losses, carbon nanofibre corrosion, and side product formation. ReagentsChemical reagents such as Na 2 SO 4 , (NH 4 ) 2 SO 4 , Na 2 (C 2 O 4 ), and NaOH were obtained from Sigma-Aldrich in analytical reagent grade and used without further purification. Demineralised and

Direct electrochemical oxidation of ammonia on graphite as a treatment option for stored source-separated urine

“…It cannot be excluded that NO and N 2 O were formed, as was found at BDD (Michels et al, 2010). However, it was demonstrated that the main gaseous nitrogen product from direct ammonia oxidation is molecular nitrogen (Webster et al, 2012;Michels et al, 2010). Thus, it is very likely that N 2 was the main gaseous nitrogen compound in our experiments.…”

“…Since the total charge was 1.65 Ah, the mineralization of graphite could account for about one third of the anodic current. The competition of direct ammonia oxidation, CO 2 formation and oxygen evolution on carbon fibers was pointed out by Webster et al (2012). The low current efficiency for ammonia oxidation therefore most probably resulted from a combination of organics oxidation, graphite mineralization and oxygen evolution.…”

Fast-Scan Cyclic Voltammetry: Chemical Sensing in the Brain and Beyond

“…37 Indeed, scanning to a potential of +1.3 V has been shown to etch the carbon surface at a rate of 0.24 nm/min (~70 femtometer/voltammogram), 26 presumably by way of carbon dioxide generation at the electrode surface. 103…”

Carbon Nanofibers Provide a Cationic Rectifier Material: Specific Electrolyte Effects, Bipolar Reactivity, and Prospect for Desalination

“…Carbon nanofibers provide robust but highly porous films with high surface area and convenient synthesis often based on bio‐resources . They are readily obtained with negative surface charge and deposited from suspension into mechanically robust porous films . Carbon nanofibers (CNFs) represent a class of carbon nanomaterials with a fibrous (and sometimes tube‐like) structure that is relatively cheap and easy to synthesize .…”

“…[26] They are readily obtained with negative surface charge and deposited from suspension into mechanically robust porous films. [27] Carbon nanofibers (CNFs) represent a class of carbon nanomaterials with a fibrous (and sometimes tube-like) structure that is relatively cheap and easy to synthesize. [28] A common synthetic route to CNFs is based on electrospinning of polymer solutions (e. g. poly-acrylonitrile or poly-pyrrole in an organic solvent such as DMF) followed by carbonization in the presence of inert gas.…”