Anodic oxidation current

Carbon Monoxide The presence of CO in a H2-rich fuel has a significant effect on anode performance because CO affects Pt electrodes catalysts. The poisoning is reported to arise from the dual site replacement of one H2 molecule by two CO molecules on the R surface (40, 41). According to this model, the anodic oxidation current at a fixed overpotential, with (ico) and without (in2) CO present, is given as a function of CO coverage (0co) by Equation (5-11) ... 

In addition, in the graphical presentation of data, different conventions are used, giving rise to problems in the interpretation and comparison of results. However, a good convention will not cause any problems. In this book (Fig. 1.2) positive potentials are directed to the right of the origin, and anodic (oxidation) currents are taken as positive (directed upward from the... 

LaNi03 shows two-dimensional semiconducting character which would be responsible for the C 2 vs. E plots. Similar results have been reported for the reduction of Fe(CN)g" on Pb02 in 0.5MK2SO4 solutions by Lovrecek et. al [89]. While diffusion-controlled anodic oxidation currents on Pb02 are the same as on platinum, at potentials below 0.175 V vs. SCE where reduction of the oxide surface becomes noticeable, cathodic currents fall to very small values and the j-E curve shows a maximum. 

Fourier transform infrared reflectance spectrum (FTIR) results indicate that AChE was immobilized successfully on the MWCNT/PDDA surface. CV results show that electrooxidation of thiocholine occurs at a much lower oxidation potential +0.55 V at MWCNT/GCE and the electrooxidation current is ten times higher than that of bare GCE. In addition, amperometric results show that the response of thiocholine at MWCNT/GCE was 200 times more than that of bare GCE. This significant enhancement in the anodic oxidation current of the enzymatic product thiocholine can be attributed to the fast electron transfer and... 

The variant described under (iv) has been the most thoroughly studied. Between pH 5 and 9 the anodic oxidation current of hydrazine at +100 mV vs SCE (in the Tafel region) depends linearly on OH concentration ... 

Karube et al. (1977c) proposed a biofuel cell containing Clostridium butyricum cells for BOD assay. The anodic oxidation current of hydrogen and formate anaerobically formed from organic compounds was used as the measuring signal. 

At equilibrium, the rates of the anodic and cathodic partial reactions are equal, i.e., there is no net change of the inventory of Red and Ox. When the system is perturbed such that the electrode potential is positive with respect to the equilibrium potential, the rate of the anodic partial reaction is greater than that of the cathodic partial reaction. The electrode reaction exhibits a net anodic (oxidation) current. Likewise, for perturbations negative to the equilibrium potential, the electrode reaction exhibits... 

The difference is discussed in the succeeding text.) Within the voltage range of 0 to -0.3 V versus SCE only a small residual current flows. It is conventional in polarography to represent cathodic (reduction) currents as positive and anodic (oxidation) currents as negative. The residual current actually comprises two components, a faradaic contribution and a charging or double-layer current contribution ... 

In 1948 Kalousek introduced the commutator method to establish the reversibility of certain inorganic and organic redox processes. In this method, the electrode potential is alternately switched from a potential at which the reduction product is formed to that potential at which it is reoxidized (cf. cyclic voltammetry). The mean current is recorded against the increasing potential and, for a polarographically reversible process, the observed cathodic (reduction) current is equal but opposite to the anodic (oxidation) current. 

At a time t, less than T the cathodic reduction current is replaced with an anodic oxidation current, causing the reoxidation of the R species obtained during reduction. A reverse potential time curve is observed, with a reverse transition time T. For the case in which i = -i, one obtains the relation ... 

Thus, at anode, oxidation current is dominant. The negative sign indicates net oxidation wherein the electrons are leaving the electrode. For cathode, the overpotential is negative hence, the second term on the right-hand side of the cathode current density equation (Equation 5.108) is negligible in comparison with the first term. The cathode current density reduces to... 

The effect of CNT on the current response due to NO2 is shown in F ire 3.35. It exhibits a remarkable increase in the amperometric response from the modified electrode consisting of CNT when compared to that without CNT. Furthermore, with N02 (500 pM), the increase in the anodic oxidation current observed at the SODl-CNT-PPy-Pt electrode was fivefold greater than that of the CNT free... 

The metal atom is oxidised and forms M" ions that are released in the aqueous phase. This creates a flux of electrons within the metal in the direction solution — metal. The resulting anodic oxidation current 4 flows from the metal to the solution. 

A number of papers describe techniques for the determination of choline esterase activity based on amperometric measurement of the product formed as a result of enzymatic hydrolysis. The oxidation potential of choline is too high to be electro-chemically oxidized directly. In this case, artificial (nonnative) choline esterase substrates are used. Thus, butyiyl or acetyl thiocholine forms thiocholine as a result of choline esterase hydrolysis. When the analyte is not present in the solution, the substrate acetylthiocholine is converted into thiocholine and acetic acid. Thiocholine is oxidized by the appUed voltage. In the presence of an inhibitor, conversion of acetylthiocholine is decreased or even null. Furthermore, the anodic oxidation current is inversely proportional to the concentration of pesticides in samples and the exposed time as well. The procedure of the preparation of an AChE biosensor and pesticide detection is shown in Fig. 13.4. 

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