Ethanol tolerant cathodes

Savadogo O, Rodriguez Varela FJ (2008) Palladium-alloy catalysts as ethanol tolerant cathodes for direct alcohol fuel cell applications. J New Mater Electrochem Syst 11 69-74... 

Nanostrutured Electrocatalysts for Methanol and Ethanol-Tolerant Cathodes... 

The performance characteristic of a DEFC employing 1 mg/cm 20 % Pt3Cri/C ethanol tolerant ORR catalyst at the cathode and 20 % PtSn/C at the anode is shown in Fig. 3.5. Non-preheated ethanol was pumped to the anode side without backpressure at a flow rate of 2 ml/min. The performance curves at 60 °C and 90 °C are presented. The expected enhancement in cell voltage vs. current density performances is observed with the increased temperature in Ref. [19]. 

Rodriguez Varela EJ, Savadogo O (2009) Ethanol-tolerant Pt-alloy cathodes for direct ethanol fuel cell (DEEC) applications. Asia-Pac J Chem Eng 4 17-24... 

Rodriguez Varela FJ, Gaona Coronado AA, Jiang Q-Z, Bartolo Perez P (2011) Pt-CeOx/ MWCNT electrocatalysts as ethanol-tolerant ORR cathodes for direct alcohol fuel cells. J New Mater Electrochem Syst 14 75-80... 

One of the main issues in the direct alcohol fuel cells (DAFCs) is that the fuel can easily permeate into the cathode through the proton exchange membrane, which causes dramatic performance loss since the currently used Pt-containing cathode catalysts have no or little methanol tolerance. One of the advantages of Pd-M alloys over Pt in DAFCs is their high methanol and ethanol tolerance in acid. In particular, methanol tolerance was demonstrated for Pd-Fe, Pd-Co, Pd-Cr, Pd-Ni, and Pd-Pt alloys [19, 41, 53, 77-80]. 

Preparative scale reduction of oximes at a mercury or lead cathode in acid solution has been used in the conversion of the carbonyl function to amine. Originally, 30-50% sulphuric acid was used as solvent [195] but ethanol with dilute hydrochloric acid is usually satisfactory. Aliphatic and aromatic oximes give amines in 64-86% yields [196]. Aromatic ketoximes are also reducible in alkaline solution and acetophenone oxime has been converted to 1-phenylethylamine in a tri-potassium orthophosphate solution [197], The reduction of oximes in acid solution is tolerant of many other substituents as indicated by a number of examples [198, 199, 200. Phenylglyoxa monoxime in acid solution is however reduced at both the carbonyl and the oxime centres by sodium amalgam to yield 2-amino-1-phenylethanol [201]... 

Tsivadze AY, Tarasevich MR, Kuzov AV, Romanova lA, Pripadchev DA (2008) New nanosized cathode electrocatalysts tolerant to ethanol. Doklady Phys Chem 421 166-169... 

In the case of DEFC, Piipadchev and co-authors [28] developed platinum-based (Pt/C) cathode catalysts modified with S, P, and Bi that were highly tolerant to ethanol crossover into the cathode compartment of the fuel cell. In the case of doping Pt/C with these elements, the researchers used ttiphenylphosphine, bismuth nitrate, and thiourea as dopant sources. The catalysts were synthesized by high-temperature treatment of the catalyst-dopant element mixture in an inert atmosphere (further details see Ref. [28]). 

Different from the results on Pt, the curves demonstrate the very high tolerance of the Pd-based catalysts to ethanol during the ORR. According to the authors, this phenomenon might be related to the inactivity of Pd and/or Co for ethanol oxidation reaction, and this might be due to the absence of adsorption of the alcohol and/or intermediate reaction species onto the catalyst surface. So, these results indicate that the utilization of Pd-aUoys as cathode catalysts in a DEFC will help in reducing the high increase in cathode overpotential observed on Pt catalysts due to the ethanol crossover. 

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