Iridium Application in Low‐Temperature Acidic Fuel Cells: Pt‐Free Ir‐Based Catalysts or Second/Third Promoting Metal in Pt‐Based Catalysts?

Antolini, Ermete

doi:10.1002/celc.201300049

Cited by 20 publications

(15 citation statements)

References 99 publications

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“…However, studies show a considerable decrease of the PtRu anode activity in a DMFC due to depletion of Ru 60 , 61 . For this reason, PtIr catalysts are attracting considerable interest due to their higher stability and comparable activity with respect to PtRu 62 – 67 . Pt and Ir atoms can be combined to form solid solutions and enhance the activity towards the MOR due to their bifunctional effect.…”

Section: Resultsmentioning

confidence: 99%

On the pH Dependence of the Potential of Maximum Entropy of Ir(111) Electrodes

Ganassin

Sebastián

Climent

et al. 2017

Sci Rep

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Studies over the entropy of components forming the electrode/electrolyte interface can give fundamental insights into the properties of electrified interphases. In particular, the potential where the entropy of formation of the double layer is maximal (potential of maximum entropy, PME) is an important parameter for the characterization of electrochemical systems. Indeed, this parameter determines the majority of electrode processes. In this work, we determine PMEs for Ir(111) electrodes. The latter currently play an important role to understand electrocatalysis for energy provision; and at the same time, iridium is one of the most stable metals against corrosion. For the experiments, we used a combination of the laser induced potential transient to determine the PME, and CO charge-displacement to determine the potentials of zero total charge, (EPZTC). Both PME and EPZTC were assessed for perchlorate solutions in the pH range from 1 to 4. Surprisingly, we found that those are located in the potential region where the adsorption of hydrogen and hydroxyl species takes place, respectively. The PMEs demonstrated a shift by ~30 mV per a pH unit (in the RHE scale). Connections between the PME and electrocatalytic properties of the electrode surface are discussed.

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Section: Resultsmentioning

confidence: 99%

On the pH Dependence of the Potential of Maximum Entropy of Ir(111) Electrodes

Ganassin

Sebastián

Climent

et al. 2017

Sci Rep

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“…This can result in a loss in the oxygen reduction reaction (ORR) activity as well as in membrane degradation, leading to a decrease in the cell potential by as much as 200 mV. [6][7][8] Pt x Ir y has been proposed as a promising alternative to Pt x Ru y , as Ir is more resistant to dissolution 9,10 than Ru and as the presence of Ir has been reported to enhance the MOR activity (vs. Pt alone) in binary, [11][12][13][14][15][16][17] ternary, 16,18,19 and quaternary 20 alloy catalysts. Contrary to Pt-Ru, Pt x Ir y has also been reported to have good catalytic activity toward the oxygen reduction reaction (ORR), which occurs at the DMFC cathode.…”

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confidence: 99%

Understanding the Role of Ir during Methanol Oxidation at Pt_xIr_yAlloy Nanoparticles

Sawy

Birss

2017

J. Electrochem. Soc.

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The formation of Pt x Ir y alloy nanoparticles (NPs), having a controlled bulk and surface composition over a wide range of Ir content (35-90 at% Ir), was reported in our recent work. While this prior work did examine the activity of these NPs toward the methanol oxidation reaction (MOR), this was done only per mass of catalyst and only under RT conditions. Here, the MOR activity is reported based on the real surface area of the NPs, determined using several electrochemical methods as well as TEM analysis, in both room temperature (RT) and 60 • C methanol-containing 0.5 M H 2 SO 4 solutions. These more comprehensive results suggest that the bi-functional effect of Ir on Pt activity plays the most significant role in catalyzing the MOR, with the optimum Ir content found to be ca. 35 at% and 50 at% at low and high potentials, respectively, at both temperatures. This demonstrates that less Ir is needed when the CO production rate is low, as is the case for methanol oxidation at the low potentials desired in operating direct methanol fuel cells.

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“…The addition of metal oxides to Pt catalysts can provide an enhancement of the water displacement reaction at lower over-potentials. 7,8 Literature studies have underlined the importance of both nature and strength of adsorbed oxygen species in the methanol oxidation process. 9 Unfortunately, water discharging occurs at high potentials on the Pt surface.…”

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confidence: 99%