Bimetallic and Ternary Alloys for Improved Oxygen Reduction Catalysis

Nilekar, Anand Udaykumar; Xu, Ye; Zhang, Junliang; Vukmirovic, Miomir B.; Sasaki, Kotaro; Adžić, Radoslav R.; Mavrikakis, Manos

doi:10.1007/s11244-007-9001-z

Cited by 214 publications

(207 citation statements)

References 31 publications

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“…In fact, as the Fe content gets larger the OH adsorption on Pt sites is increasingly inhibited but the number of Pt sites available on the surface decreases. Consequently, the larger ORR activities observed for PtFe/C catalysts of compositions Pt:Fe 80:20 and 70:30 would result of the opposite effects on ORR activity of the number and OH coverage of Pt sites, as suggested by Nilekar et al 61 ORR in the presence of methanol.-Pt/C electrocatalysts suffer severe losses of performance for the ORR in the presence of methanol caused by the crossover of the alcohol through the proton exchange membrane. Thus, methanol-tolerant catalysts for ORR are needed to improve the performance of direct methanol fuel cells.…”

Section: Resultsmentioning

confidence: 94%

Well-Alloyed PtFe∕C Nanocatalysts of Controlled Composition and Same Particle Size: Oxygen Reduction and Methanol Tolerance

Malheiro

Perez

Villullas

2009

J. Electrochem. Soc.

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A study of the effect of iron concentration on the electrocatalysis of oxygen reduction reaction ͑ORR͒ on well-alloyed carbonsupported PtFe nanocatalysts with a controlled iron content and the same particle size is presented. To obtain the catalysts for this study, PtFe nanoparticles of different compositions were first obtained in a colloidal state in sodium bis͑2-ethylhexyl͒sulfosuccinate ͑AOT͒+n-butanol/n-heptane/water microemulsions and subsequently supported in high surface area carbon powder. Transmission electron microscopy evidenced that all PtFe/C nanocatalysts prepared are monodispersed and have nearly the same average particle size. X-ray diffraction studies showed that the lattice parameter of these PtFe/C catalysts varies linearly with iron content up to 50% ͑in atoms͒, while the compositions of the alloyed phases estimated by using Vegard's law are almost identical to the nominal values, indicating a high degree of alloying. The electrocatalytic activity for ORR of these catalysts was studied using the rotating disk electrode technique in O 2 saturated 0.5 mol L −1 H 2 SO 4 solutions, while methanol tolerance was evaluated from curves taken in acid solutions containing 0.1 mol L −1 methanol. The results reported here reflect the dependence of the electrocatalytic activity for the ORR on iron concentration in the absence of particle size effects and metal segregation. The growing awareness of the risks related to human-induced climate change has considerably raised the necessity of alternative ways of energy production. In this context, the conversion of chemical energy into electricity has become increasingly important and, thus, clean and efficient devices such as fuel cells are now attracting a great deal of attention from governments, academic institutions, and private businesses. While fuel cells might help to overcome the power problems, there are still a number of issues to be worked out to make the generation of electrical power using fuel cells practical and cost-effective.Among the different fuel cell types, the proton exchange membrane fuel cell ͑PEMFC͒ is considered the most adequate for vehicle and portable applications. However, much needs to be done to improve the performance. Among other problems, the slow kinetics of the oxygen reduction reaction ͑ORR͒ remains one of the key factors affecting the performance of PEMFCs, causing overpotential losses of ϳ0.3 to 0.4 V under typical operation conditions.

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Section: Resultsmentioning

confidence: 94%

Well-Alloyed PtFe∕C Nanocatalysts of Controlled Composition and Same Particle Size: Oxygen Reduction and Methanol Tolerance

Malheiro

Perez

Villullas

2009

J. Electrochem. Soc.

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“…Such alloys have been shown to have desirable properties for other electrochemical reactions, especially oxygen reduction. [50][51][52][53][54][55] In this case, supporting Cu 3 Pt 1 on Pt, for example, would subject the surface alloy layer to an expansive strain; thus, Pt and Cu would be more reactive on this surface than the corresponding bulk alloy. The stronger adsorbate binding on such a surface would move the Cu 3 Pt 1 point towards the ideal point on the volcano plot.…”

Section: Surface Alloys Of Ptcumentioning

confidence: 99%

Bifunctional anode catalysts for direct methanol fuel cells

Rossmeisl

Ferrin

Tritsaris

et al. 2012

Energy Environ. Sci.

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166

126

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Using the binding energy of OH* and CO* on close-packed surfaces as reactivity descriptors, we screen bulk and surface alloy catalysts for methanol electro-oxidation activity. Using these two descriptors, we illustrate that a good methanol electro-oxidation catalyst must have three key properties: (1) the ability to activate methanol, (2) the ability to activate water, and (3) the ability to react off surface intermediates (such as CO* and OH*). Based on this analysis, an alloy catalyst made up of Cu and Pt should have a synergistic effect facilitating the activity towards methanol electro-oxidation. Using these two reactivity descriptors, a surface PtCu 3 alloy is proposed to have the best catalytic properties of the Pt-Cu model catalysts tested, similar to those of a Pt-Ru bulk alloy. To validate the model, experiments on a Pt(111) surface modified with different amounts of Cu adatoms are performed. Adding Cu to a Pt(111) surface increases the methanol oxidation current by more than a factor of three, supporting our theoretical predictions for improved electrocatalysts.

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“…The principal approach to achieve this is to alloy platinum with some non-noble transition metal such as V, Cr, Fe, Ni, Co, Cu [1,2,3,4,5] or similarly, deposit thin metal overlayers onto less noble metal substrates [6,7,8]. Readily, great activity enhancements for the oxygen reduction reaction (ORR) have been reported for such catalysts.…”

Section: Introductionmentioning

confidence: 99%