The ethanol electro-oxidation at gas diffusion electrodes made of different catalysts, Pt/C, PtRu͑1:1͒/C, and PtSn͑7:3͒/C, were studied by on-line differential electrochemical mass spectrometry in a wide temperature range ͑30-90°C͒ as a function of the anode potential, the fuel concentration, and catalyst loading. The CO 2 current efficiency ͑CCE͒ of the ethanol oxidation reaction ͑EOR͒ exhibits a maximum at about 0.6 V and decreases rapidly with further increasing potentials. The CCE for the EOR goes down with the increase in concentration of ethanol. CCE for ethanol oxidation reaction shows a strong increase with increasing catalyst loading. The CCE increases with increasing temperature, exceeding 75% at 90°C, 0.1 M ethanol, and 5 mg/cm 2 Pt catalyst loading. PtSn/C shows high CCE, like Pt/C. But PtRu/C exhibits very small CCE. Of the intermediates, acetaldehyde is quite active for further oxidation. But acetic acid is fairly resistant against further oxidation. Our results indicate that the C-C bond scission observed for the EOR with CCE in excess of 50% has to proceed in parallel with ethanol oxidation to either acetaldehyde or acetic acid, and not sequentially from acetic acid further on, as acetic acid cannot be oxidized any further.

The fuel cell differential electrochemical mass spectrometry (FC‐DEMS) measurements were performed for studying the ethanol oxidation reaction (EOR), using alkaline membrane electrode assemblies (MEAs) made up of nanoparticle Pt catalyst and alkaline polymeric membranes. The obtained results indicate that in an alkaline medium, ethanol undergoes significantly more complete electro‐oxidation to CO2 than in an acidic MEA using the same Pt anode. The CO2 current efficiency (CCE) can be compared for acidic and alkaline MEA with similar electrochemical active area on the anode side. The CCE estimated, in case of alkaline MEA with Pt anode, is around 55% at 0.8 V/RHE, 60 °C and 0.1 M ethanol. In comparison, under similar conditions, acidic MEAs using the same anode catalyst show only 2% CCE. This might indicate that the C–C bond scission rates are much higher in alkaline media. However, the mechanism of ethanol oxidation in alkaline media is not exactly known. CO2 produced in electrochemical reaction forms soluble carbonates in the presence of aqueous alkaline electrolyte. This makes it difficult to study ethanol oxidation in alkaline media using FTIR or model DEMS systems. The alkaline polymer electrolyte membranes as used in this study for making alkaline MEAs provide an important opportunity to observe CO2 produced during EOR using FC‐DEMS system.

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A transition metal complex, oxovanadium(IV) salen (where salen represents N,N -bis(salicylidene)ethylenediamine) is immobilized on glassy carbon (GC) electrodes and utilized for electrocatalytic oxidation of cysteine. In presence of oxovanadium(IV) salen, increased oxidation current is observed due to the effective oxidation of cysteine by the electrogenerated oxovanadium(V) salen species. The oxidation current linearly varies with the concentration of cysteine from 0.1 to 1.0 mM. The modified electrode has good sensitivity and low limit of detection. These properties make the oxovanadium(IV) salen as an effective electrocatalyst for the determination of cysteine.