Hydrogen adsorption on Pt and Rh electrodes and blocking of adsorption sites by chemisorbed sulfur

Zolfaghari, Alireza; Villiard, Francis; Chayer, Martine; Jerkiewicz, Gregory

doi:10.1016/s0925-8388(96)03096-4

Cited by 44 publications

(36 citation statements)

References 21 publications

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“…The charges Q O with the oxidation and reduction of platinum. The CV curve was similar to that reported for a polycrystalline platinum electrode with a smooth surface, [22][23][24] and therefore exhibited the same electrochemical characteristics despite the sulfur and boron inclusion.…”

Section: Resultssupporting

confidence: 80%

Stabilization of an Electroless Platinum Plating Bath Using S-Bearing Additives

Mizuhashi

Cordonier

Honma

et al. 2015

J. Electrochem. Soc.

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Moderation of an electroless platinum plating bath by thiol, thioether, disulfide, thiocarbonyl, thiosulfate and sulfide compounds was investigated. The inhibitory effect of stabilizers on catalyzed anodic oxidation of the reducing agent used, sodium borohydride, on platinum surfaces was electrochemically characterized by linear sweep voltammetry. Catalytic oxidation inhibition was found to correlate with chemisorption dynamics to catalytic sites on the platinum surface and the steric structure of the sulfur in the compound. Evaluation of the compounds as moderators in electroless plating revealed that the deposition rate and bath stability correlated with the sodium borohydride oxidation inhibition character. Tiopronin had a moderate inhibitory effect on catalytic sodium borohydride oxidation and functioned as an effective stabilizer in the electroless platinum plating bath. Based on the correlation, an inhibitor concentration optimization method using anodic polarization curves was established. The dynamics of the electroless plating reaction concurred with electrochemical analysis and was comprehensively described by the mixed potential theory. Using cyclic voltammetry, the deposits had similar electrochemical characteristic to that of pure polycrystalline platinum, although less than 0.5 wt% sulfur inclusion was confirmed by elemental analysis. Platinum has unique and exploitable physical and chemical properties such as corrosion resistance, thermal stability and catalytic activity for various chemical reactions. This noble metal has been widely used in various fields, functioning as catalyst, especially in autocatalysis and fuel cells, as a sensor material and as an electrode material. Electroless deposition of nanostructured platinum for application as an electrocatalyst has also been studied.2,3 However, there are few reports in the scientific literature on the electroless plating bath itself. This may be because electroless deposition of platinum is more difficult to control than that of other noble metals such as gold or palladium. 4 Electroless plating has been used to functionalize the surface of a material and has the potential to enable fabrication of many kinds of device. Therefore a deeper understanding of electroless platinum plating may provide fabrication tools for applications not currently feasible.Studies on electroless platinum deposition or plating baths often utilize hydrazine as the reducing agent. 5,6 The platinum deposits obtained from hydrazine plating baths had excellent purity, however, aside from the discernable odor, hydrazine has been proven harmful to the human body.7 Alternatively, autocatalytic platinum plating with sodium borohydride (SBH) as a reducing agent has been reported. 8,9 In these studies, sulfur compounds such as rhodanine (Figure 1) 8 and thiols like trithiocyanuric acid 9 had been used as stabilizers of the plating bath. However, the stabilization mechanism of the sulfur compounds and identification of effective structures and optimal parameters remains unclear. ...

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Section: Resultssupporting

confidence: 80%

Stabilization of an Electroless Platinum Plating Bath Using S-Bearing Additives

Mizuhashi

Cordonier

Honma

et al. 2015

J. Electrochem. Soc.

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“…72 Even given the very low metal loading of rhodium on carbon (5 wt %), leading to difficulties to distinguish between pseudo-capacitive (from Rh) and double layer currents (from carbon support), the Rh/C catalyst reproduces the behavior observed on Rh pc electrodes. [78][79][80] The H-UPD region can be resolved in the RDE experiment, with an onset at 0.1 V RHE , but not in fuel cell due to the high onset potential of the HER (already discussed above). For these reasons, the H-UPD charge density cannot be used for the determination of the surface area of the Rh/C catalyst.…”

Section: Resultsmentioning

confidence: 94%

Hydrogen Oxidation and Evolution Reaction Kinetics on Carbon Supported Pt, Ir, Rh, and Pd Electrocatalysts in Acidic Media

Durst

Simon

Hasché

et al. 2014

J. Electrochem. Soc.

455

459

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The hydrogen oxidation and evolution reaction (HOR/HER) behavior of carbon supported metal (Pt, Ir, Rh, Pd) nanoparticle electrocatalysts is studied using the H 2 pump approach, in a proton exchange membrane fuel cell (PEMFC) setup. After describing the best method for normalizing the net faradaic currents to the active surface area of the electrodes, we measure the HOR/HER kinetic parameters (exchange current densities and transfer coefficients) in a temperature range from 313 K to 353 K and calculate the activation energy for the HOR/HER process. We compare the measured kinetic parameters with those extracted from different mass-transport limitation free setups in literature, to evaluate the hydrogen electrocatalysis on these most active surfaces. The HOR/HER activity scales with the following: Pt > Ir Rh > Pd. The anodic and cathodic transfer coefficients are similar for all metals (ca. 0.5), leading to Tafel In the current view of energy conversion based on the use of fuel cells and electrolyzers, the hydrogen electrocatalysis plays a central role. H 2 is used as a fuel in proton exchange membrane fuel cells (PEMFCs), where it is electrochemically oxidized at the anode electrode according to:In PEMFC anode electrode, only small amounts of Pt (ca. 0.05 mg Pt /cm 2 geo ) are required to catalyze the hydrogen oxidation, without contributing to any efficiency loss of the overall fuel cell performance.1 The same would hold true for the hydrogen evolution reaction -HER -at the cathode side of water electrolyzer systems. Moreover, except when considering contamination issues e.g. due to the presence of CO in reformate hydrogen, or stability issues e.g. due to hydrogen starvation events mode, a replacement of the current carbon supported platinum (Pt/C) based electrode technology is not contemplated in PEMFC. 2 The drawback of both PEM-based fuel cells and electrolyzer systems arise from the large amounts of noble metal (ca. ≈0.4 mg metal /cm 2 geo ) required to catalyze at acceptable rates the sluggish oxygen reduction reaction (ORR) in fuel cell cathodes, and the oxygen evolution reaction (OER) in electrolyzer anodes. [3][4][5] Contrary to the acidic PEM-based technologies, anion exchange membrane (AEM) based devices, [6][7][8] which are operating at high pH, offer the use of cost-effective non-noble metal electrodes to catalyze the ORR 9,10 and OER 11-13 at almost similar rates than on noble metal electrodes in acidic electrolytes. As a result, a replacement of PEMbased devices by AEM ones will be advantageous 14 if and only if AEM conductivities will be further increased to the level of PEM, 15,16 and their sensitivity to CO 2 significantly reduced. 17 However, getting rid of the noble metal contents in AEM-device electrodes would be feasible only in the case of similar hydrogen oxidation and evolution reaction (HOR/HER) rates in AEMs versus PEM-based conversion devices. Unfortunately, recent studies have shown that the HOR/HER rates of noble metal electrodes in the alkaline environment are much slower than in ...

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“…The S was deposited on Pt NPs using a spontaneous deposition process. [4,[13][14][15] After being subjected to multiple cleaning potential cycles (~30), the Pt NP-coated GC electrode was immersed in 1 mm Na 2 S (Aldrich) solution for times of 12, 30, 60, 120, 300, 600, and 1200 s, followed by rinsing with copious Milli-Q water. The S solutions were freshly prepared just before S deposition.…”

Section: Methodsmentioning

confidence: 99%

“…Although monomeric S, [4,[13][14][15] diatomic S [8-10, 16, 17] and polymeric (or multilayer) S [6,18,19] structures on Pt electrodes have been proposed, no consensus has been reached on the exact chemical state of adsorbed S.…”

mentioning

confidence: 99%

Chemical State of Adsorbed Sulfur on Pt Nanoparticles

Park

Atienza

et al. 2011

ChemPhysChem

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Adsorption of sulfur (S)-containing molecules on Pt has attracted much interest in heterogeneous catalysis in general, and in electrocatalysis in particular, because of its widely observed strong negative effect on catalytic activity. It is generally believed that the PtÀS bond is predominantly covalent and the adsorbed S (S ads ) induces a significant depletion in the d-electron population of Pt.[1] The S ads on Pt can act as a site-blocking species and/or modify the band structure of the metal resulting in a significant decrease in the reactivity of the Pt surface toward small molecules (e.g. CO, H 2 , C 2 H 4 ).[2] While the effect of the former is usually very localized, that of the latter can be long range. For instance, the adsorption of hydrogen (H) is totally inhibited by S ads before full-monolayer coverage of S ads is reached. The estimated numbers (N S ) of H adsorption sites blocked by one S atom at very low S coverage are 12 AE 3 for Pt (110) and 10 AE 1 for Pt (111), although the corresponding saturation coverages (q s ) are 0.8 and 0.62, respectively. [3,4] In contrast, a much lower N S (~2 to 3) was reported on polycrystalline Pt, indicating that the influence of the PtÀS bond is sensitive to the surface structure. [5,6] Recent studies have also shown that S ads on carbon-supported Pt (Pt/C) nanoparticles (NPs) substantially impedes the oxygen reduction reaction (ORR) and hydrogen oxidation reaction (HOR). [7,8] In particular, the S ads enhanced the formation of the deleterious H 2 O 2 by-product during the ORR. On the other hand, S ads has also been shown to enhance the activity of Pt as a site-modifier in formic acid, formaldehyde and methanol electro-oxidation. [9][10][11][12] Multiple mechanisms have been proposed for the enhancement including the entropy effect, [9] the chemical state of S ads [11] and the reduction effect. [12] A similar enhancement was also observed by a partial anodic stripping of the S ads layer and attributed to a transformation of the S adsorption structure.[9] Furthermore, the structure of the S ads , deposited from a liquid S-containing solution, was investigated by determining the anodic charges associated with the S electro-oxidation (S-EO) process. Although monomeric S, [4,[13][14][15] diatomic S [8-10, 16, 17] and polymeric (or multilayer) S [6,18,19] structures on Pt electrodes have been proposed, no consensus has been reached on the exact chemical state of adsorbed S.It is clear that in order to understand the chemistry behind these unclear and sometimes contradictory observations, unambiguous identification of the chemical state of the S ads is highly desirable. Herein we report a detailed electrochemical (EC) study of S adsorption on commercial carbon-supported Pt (Pt/C) and Pt black (Pt-B) NPs as a function of the S coverage substantiated by in situ surface enhanced Raman spectroscopy (SERS) and density functional theory (DFT) calculations of related model molecules. The NP sizes in Pt/C and Pt-B were about 4 nm and 7 nm respectively. The S coverage was cont...

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Hydrogen adsorption on Pt and Rh electrodes and blocking of adsorption sites by chemisorbed sulfur

Cited by 44 publications

References 21 publications

Stabilization of an Electroless Platinum Plating Bath Using S-Bearing Additives

Stabilization of an Electroless Platinum Plating Bath Using S-Bearing Additives

Hydrogen Oxidation and Evolution Reaction Kinetics on Carbon Supported Pt, Ir, Rh, and Pd Electrocatalysts in Acidic Media

Chemical State of Adsorbed Sulfur on Pt Nanoparticles

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