A DEMS and cyclic voltammetry study of NH3 oxidation on platinized platinum

Gootzen, Jfe; Wonders, AH Ad; Visscher, Whm Wil; Santen, van Ra Rutger; Veen, van Jar Rob

doi:10.1016/s0013-4686(97)00285-5

Cited by 118 publications

(114 citation statements)

References 19 publications

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“…Figure 3 shows the calculated concentration ratio of NH 3 , NH The concentration effect of carbonate ion species on NH 3 oxidation current over Pt/C electrode was investigated by cyclic voltammetry. 4 In the positive scan at 0.35-0.40 V, only the charging current of electric double layer was observed, of which value was identical to that detected in the absence of NH 3 in the electrolyte solution. The onset potential of ammonia oxidation ca.…”

Section: Resultssupporting

confidence: 60%

“…[1][2][3] Ammonia can be oxidized over platinum electrocatalysts in an alkaline aqueous solution at room temperature. [4][5][6][7][8] The anion exchange membrane (AEM) is an alkaline polymer containing quaternary ammonium or pyridinum function groups as ion exchange sites. In the previous report, we have demonstrated the direct ammonia fuel cell (DAFC) employing the OH-form AEM as an electrolyte and Pt/C as a cathode at 50…”

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confidence: 99%

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Effect of Carbonate Ion Species on Direct Ammonia Fuel Cell Employing Anion Exchange Membrane

Suzuki¹,

Muroyama²,

Matsui³

et al. 2016

J. Electrochem. Soc.

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The effect of carbonate ion species on the direct ammonia fuel cell (DAFC) employing anion exchange membrane (AEM) was evaluated. The OH-form and HCO 3 -form AEMs were applied as electrolytes for DAFCs. The obtained current density of DAFC with HCO 3 -form AEM was 1/7 of that with OH-form AEM. This is because carbonate ion species in the AEM suppress the ammonia oxidation reaction on Pt/C anode. Under the presence of carbonate ion species in the electrolyte, the ammonium ion and carbamate ion were formed accompanied with a reduction in the ammonia concentration in the vicinity of anode. Recently, ammonia has been attracted much attention as a fuel for fuel cells due to its low production cost, ease in liquefaction at ambient temperature, and high energy density.1-3 Ammonia can be oxidized over platinum electrocatalysts in an alkaline aqueous solution at room temperature. [4][5][6][7][8] The anion exchange membrane (AEM) is an alkaline polymer containing quaternary ammonium or pyridinum function groups as ion exchange sites. In the previous report, we have demonstrated the direct ammonia fuel cell (DAFC) employing the OH-form AEM as an electrolyte and Pt/C as a cathode at 50• C. 9The OCV and performance were strongly dependent on the catalytic activity of anode for ammonia oxidation; e.g., the OCVs of cells with Pt/C and Pt-Ru/C anodes were 0.37 V and 0.54 V, respectively (anode gas; NH 3 humidified at 50 o C, cathode gas; 21% O 2 -N 2 humidified at 50• C). Furthermore, the permeation of ammonia through AEM also affected the OCV and performance. This finding suggested that the permeation of ammonia is inevitable even if the anode with high activity is developed. In the practical operating condition, moreover, the ambient air containing CO 2 will be used as an oxidant. However, CO 2 is the degradation factor for the cell performance, especially anode activity on H 2 oxidation.10 This is because the carbonate ion species (CO 2− 3 , HCO − 3 ) produced in AEM by CO 2 dissolution migrate toward the anode under a current loading condition, resulting in the condensation of these anions in the vicinity of anode.10-14 So, it is of importance to reveal the influence of carbonate ion species on the ammonia oxidation reaction over the anode.In this study, the effect of carbonate ion species on the performance of the direct ammonia fuel cell was evaluated by applying the OH-form and HCO 3 -form AEMs as electrolytes. Furthermore, the electrocatalytic activity of Pt/C anode for ammonia oxidation was studied under the coexistence of carbonate and bicarbonate ions in the electrolyte. ExperimentalFuel cell test.-For the electrocatalysts, Pt/C (Pt 46.4 wt. %, Tanaka Kikinzoku Kogyo) was used as received. The membrane electrode assembly (MEA) was constructed by screen-printing the mixture of Pt/C and anion exchange ionomer (AS-4, Tokuyama Co.) on AEM. The basic properties of AEM (A201, Tokuyama Co.) used in this study and the detailed procedure of screen-printing were described in the previous report. 9 The electrode area was 5.0 cm...

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Section: Resultssupporting

confidence: 60%

mentioning

confidence: 99%

Effect of Carbonate Ion Species on Direct Ammonia Fuel Cell Employing Anion Exchange Membrane

Suzuki¹,

Muroyama²,

Matsui³

et al. 2016

J. Electrochem. Soc.

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“…To reveal the intrinsic activity of the prepared NPs, the current is normalized by the ECSA of the NPs. An anodic current peak is observed at around −0.77 V (MSE), which is attributed to the ammonia oxidation to N 2 as well as N ads [37,44,66,67]. In the previous studies, CV was measured in the absence of ammonia in the solution, and there was no such characteristic current peak [37,68].…”

Section: Resultsmentioning

confidence: 97%

Shape-controlled synthesis of Pt-Ir nanocubes with preferential (100) orientation and their unusual enhanced electrocatalytic activities

Zhong

Liu

et al. 2014

Sci. China Mater.

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Pt-Ir nanocubes with (100)-terminated facets were synthesized for the first time and their unusual high electrocatalytic activity for a model reaction (i.e., ammonia oxidation) was reported. The key parameters in controlling the shape of the PtIr nanocubes were systematically investigated by transmission electron microscopy (TEM). The electrocatalytic activities of the prepared Pt-Ir and pure Pt nanoparticles (NPs) were characterized by cyclic voltammetry (CV). The results showed that the amount of W(CO) 6 and the volume ratio of oleylamine and oleic acid play a significant role in the development of well-defined Pt-Ir nanocubes. The resultant Pt-Ir nanocubes exhibit (100) orientation, which has been confirmed by not only the structural characterization results from high-resolution TEM (HRTEM) and X-ray diffraction (XRD) but also hydrogen desorption profiles obtained from the CV measurements in H 2 SO 4 solution. Lattice contraction of the Pt-Ir nanocubes were suggested by HRTEM and XRD measurements, and the electronic interactions between Pt and Ir in the Pt-Ir nanocubes were demonstrated by X-ray photoelectron spectroscopy. The Pt-Ir nanocubes show higher specific activity than pure Pt nanocubes and much higher specific activity than the polycrystalline Pt-Ir NPs. The much improved specific activity of the Pt-Ir nanocubes could be attributed to the reason that the introduction of Ir in the Pt-Ir nanocubes largely maintains the highly active Pt (100) sites and thus a positive synergistic effect through the addition of Ir to Pt could be achieved due to the possible bifunctional mechanism and the electronic effect.

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“…The volumes of the anodic and cathodic chambers of the cell were 16.5 ml. The IrO 2 electrode was prepared by coating multiiridium oxide layers onto a Ti plate in the same way as that used in our previous work to fabricate some catalytic oxide electrodes [10][11][12]. In this experiment, an electrolyte solution of 65 ml of 0.5 M (NH 4 ) 2 SO 4 in 0.1 M Na 2 SO 4 , of which the initial pH was adjusted before each electrolytic run, was circulated into the respective reservoirs for the anolyte and catholyte solutions through the anodic and cathodic chambers.…”

Section: Methodsmentioning

confidence: 99%

Electrolytic decomposition of ammonia to nitrogen in a multi-cell-stacked electrolyzer with a self-pH-adjustment function

2006

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This paper describes a study of continuous decomposition characteristics of ammonia to nitrogen in a multi-cellstacked electrolyzer with an anion exchange membrane. The pH change of ammonia solution in both the anodic and cathodic chambers of a divided cell due to the water splitting reactions was studied together with the electrolytic decomposition of ammonia. The electrolytic decomposition efficiency of ammonia was considerably affected by the pH change of ammonia solution caused by the water splitting reactions. In the anodic chamber with the ammonia solution, the water splitting reaction which produced protons occurred at a pH of less than 8, and in the cathodic chamber, that producing hydroxyl ions occurred at a pH of more than 11. By using the characteristics of the electrolytic water splitting reactions in a divided cell, a continuous electrolyzer with a self-pH-adjustment function was devised, wherein a portion of the ammonia solution from a pH-adjustment reservoir was circulated through the cathodic chambers of the electrolyzer. This enhanced the pH of the ammonia solution being fed from a pH-adjustment reservoir into the anodic chambers of the electrolyzer, which caused a higher ammonia decomposition yield. Based on this electrolyzer, a saltfree ammonia decomposition process was suggested. In this process, ammonia in the solution was continuously and effectively decomposed into environmentally harmless nitrogen gas.

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A DEMS and cyclic voltammetry study of NH3 oxidation on platinized platinum

Cited by 118 publications

References 19 publications

Effect of Carbonate Ion Species on Direct Ammonia Fuel Cell Employing Anion Exchange Membrane

Effect of Carbonate Ion Species on Direct Ammonia Fuel Cell Employing Anion Exchange Membrane

Shape-controlled synthesis of Pt-Ir nanocubes with preferential (100) orientation and their unusual enhanced electrocatalytic activities

Electrolytic decomposition of ammonia to nitrogen in a multi-cell-stacked electrolyzer with a self-pH-adjustment function

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