Methanol oxidation activity

Crown A, Moraes IR, Wieckowski A. 2001. Examination of Pt(lll)/Ru and Pt(lll)/Os surfaces STM imaging and methanol oxidation activity. J Electroanal Chem 500 333-343. 

The same group, in a previous work, reported on the realization of a hybrid anode electrode [197]. An appreciable improvement in methanol oxidation activity was observed at the anode in direct methanol fuel cells containing Pt-Ru and Ti02 particles. Such an improvement was ascribed to a synergic effect of the two components (photocatalyst and metal catalyst). A similar behavior was also reported for a Pt-Ti02-based electrode [198]. Another recent study involved the electrolysis of aqueous solutions of alcohols performed on a Ti02 nanotube-based anode under solar irradiation [199]. 

Methanol oxidation activities have been examined on a Pt-Sn electrode. Cyclic voltammograms of a smooth Pt-Sn electrode in 3 M sulfuric acid with 1 M methanol are shown and compared with pure platinum in Fig. 4-17. 

Methanol was added while the potential of Pt-Mo electrode was held at 50 mV. Then the potential was scanned in the anodic direction. The voltammogram is shown in Fig. 4-23. At potentials lower than 500 mV, the voltammogram is almost the same as that without methanol. At higher than 500 mV, methanol oxidation current is seen but is smaller than that of pure platinum. According to Kita et odP, Pt-Mo enhances the methanol oxidation activities at lower potentials than 500 mV. However, the effect was not clearly seen in this experiment. 

Nevertheless, for a condition in which methanol oxidation to COad is faster, such as at a higher temperature or in a higher concentration of methanol, higher methanol oxidation activity would be expected because of the higher catalytic activity on COad oxidation of Pt-Ru-Sn. 

Table 1 Oxygen Chemisorption and Methanol Oxidation Activity Results on Various V205/SnQ2 Catalysts...

Figure 2. Methanol oxidation activity at 150°C as a function of ammonia uptake at 150°C on V20g/Ti02(A)...

High methanol oxidation activity is observed for Co-rich compositions that are similar to stoichiometries identified in the broad screening study (Fig. 11.17). Particular examples are Pt14Co63Ru23 or Pt18Co62Ru2o-... 

C. K. Witham, T. I. Valdez, and S. R. Narayanan, Methanol Oxidation Activity of Co-Sputter Deposited Pt-Ru Catalysts , Proceedings of the Symposium on Direct Methanol Fuel Cells, Electrochemical Society, PV 2001-4, p.l23... 

Figure 5.10b presents RDE curves obtained for the ORR in 0.5 mol H2SO4 electrolyte in the absence and presence of 1.0 mol methanol. The ORR curves for Pt/C was included in the absence of methanol for comparison. As can be observed, RuSe/C shows an increase in overpotential of c.a.lO mV, in the presence of methanol which corroborates with its low observed for methanol oxidation. For Rh cSy/C, a current contribution from methanol oxidation was seen at potentials above 0.7 V, resulting in a net positive current at above 0.8 V. As discussed by the authors [31], modifying ruthenium with selenium results in a significant enhancement of oxygen reduction activity and almost an entirely suppressing of its methanol oxidation activity, in contrast to rhodium modified by sulfur. 

Matsumoto F (2012) Ethanol and methanol oxidation activity of PtPb, PtBi, and PtBi2 intermetallic compounds in alkaline media. Electrochemistry 80(3) 132-138... 

Poly(N-methylpyrrole) has been used in several studies because of its higher stability than unsubstitut polypyrrole (24,25). A poly(N-methylpyrrole)/Nafion composite was found to be an effective support, and is attractive for use in fuel cells because of its proton conductivity (24). Incorporation of polynuclear rudienium oxide/cyanoruthenates into poly(N-methylpyirole) containing Pt particles produced a synergistic incr se in methanol oxidation activity (25). 

Daimon H, Onodera T, Nakagawa T, Nitani H, Yayamoto TA (2010) Methanol oxidation activity of nanosized PtRu catalysts and their microstructures. J Nanoelectron Optoelectron 5 1-5... 

Onodera T, Suzuki S, Takamori Y, Daimon H (2010) Improved methanol oxidation activity and stability of well-mixed PtRu catalysts synthesized by electroless plating method with addition of chelate ligands. Appl Catal A Gen 379 69-76... 

Figure 4.16. STM images of Ru-decorated Pt(lll) prepared by spontaneous deposition according to the method of Chrzanowski and Wieckowski [100]. Deposition times a) 10 s, b) 20 s, c) 40 s, and d) 90 s [99]. (Reproduced from Journal of Electroanalytical Chemistry, 500(1-2), Crown A, Moraes IR, Wieckowski A, Examination of Pt(l 11)/Ru and Pt(l 1 l)/Os surfaces STM imaging and methanol oxidation activity, 333 3, 2001, with permission from Elsevier.)...

The importance of Ru-oxides were also considered by Frelink and co-workers attributing mainly a catalytic role to Ru-oxide (Equation 4.19) since by ellipsometry the disappearance of the Ru oxide film was observed in the presence of methanol [111, 112]. The same observation was made with regard to Sn as a cocatalyst. Furthermore, based on EDX analysis it was proposed that the oxide formation on PtRu leads to (PtRu)Ox(HS04) with x 2 and y 4, and the optimum Ru surface coverage for methanol oxidation activity is 15% [112]. 

Figure 4.43. Effect of Mo content (atomic percentage) on the methanol oxidation activity of (W o)C. Legend catalyst subjected to alkaline treatment, o catalyst without alkaline treatment. Conditions 323 K, 0.5 Vj je, 1 M H2SO4, 4 M CH3OH [213]. (Reproduced by permission of ECS— The Electrochemical Society, from Kawamiua G, Okamoto H, Ishikawa A, Kudo T. Tungsten molybdenum carbide for electrocatalytic oxidation of methanol.)...

Wang C-H, Shih H-C, Tsai Y-T, Du H-Y, Chen L-C, Chen K-H. High methanol oxidation activity of electrocatalysts supported by directly grown nitrogen-containing carbon nanotubes on carbon cloth. Electrochim Acta 2006 52 1612-17. 

Typically, gold is considered to be a poor ehoice as a fuel eell electroeatalyst. However, gold would be a stable alloying element, although still expensive. PtAu alloys have been studied as potential DMFC eatalysts and have shown methanol oxidation activity [368] for specific structures. Gold catalysts are also effeetive for removing CO from H2 gas streams in reformers [369]. 

Sirk AHC, HiU JM, Kung SKY, Bitss VI. Effect of redox state of PtRu electrocatalysts on methanol oxidation activity. J Phys Chem B 2004 108 689-95. 

The methanol oxidation activation energy was also obtained according to Eqn (12.11) ... 

On the other hand, efforts are also being made to provide methanol-tolerant cathode catalysts. Electrochemically pretreated Bi Ir O is reported to be inactive toward methanol oxidation [3], In addition, electrochemically pretreated BijPtj gltj exhibits negligible methanol oxidation activity and shows activity for oxygen reduction reaction. The methanol tolerance increases as the Pt content decreases. Methanol-tolerant cathode catalysts will reduce the negative effects being caused by the diffused methanol. 

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