Structural changes of surface oxide layers on palladium

Chierchie, T.; Mayer, C.; Lorenz, W.J.

doi:10.1016/0368-1874(82)85121-6

Cited by 153 publications

(81 citation statements)

References 31 publications

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“…These values are in very good agreement with those reported in Ref. 37 and, while being less precise than those derived from lengthy CO-stripping measurements, they provided us with a fast means of quantifying the Pd-ECSA of the unstable model surfaces presented below.…”

Section: −2supporting

confidence: 89%

“…[36][37][38] The recorded voltammograms, plotted in Figure 1a, are qualitatively similar to those reported in Refs. 36 to 38; the positive-going scans feature a palladium oxidation onset at ≈0.75 V RHE followed by a peak at ≈0.85 V RHE , and the oxide reduction currents in the negative-going scans become larger and peak at lower potentials as E inversion increases.…”

Section: −2supporting

confidence: 85%

“…Nevertheless, this approach is probably the most imprecise out of these three, since the definition of an integration baseline free of pseudo-capacitive contributions is highly ambiguous, and the stoichiometry of these (hydr)oxides changes with the potential. While several works [36][37][38][39] …”

Section: −2mentioning

confidence: 99%

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Bulk-Palladium and Palladium-on-Gold Electrocatalysts for the Oxidation of Hydrogen in Alkaline Electrolyte

Henning

Herranz

Gasteiger

2014

J. Electrochem. Soc.

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The commercial feasibility of alkaline-exchange membrane fuel cells and electrolyzers passes by the development of hydrogen oxidation and evolution reaction (HOR/HER) catalysts featuring an activity and/or cost advantage over platinum, which remains the most active metal for these processes. Among these alternatives, Pd appears as a promising candidate, since its price is typically 2-3 fold lower than that of Pt. With this motivation, the first section of this study displays our attempts at quantifying the kinetic parameters of the HOR/HER on bulk Pd in 0.1 M NaOH, which were prevented by the simultaneous absorption of hydrogen into bulk palladium. We succeeded at circumventing this issue by depositing Pd-adlayers on a polycrystalline Au-substrate by galvanic displacement of underpotentially-deposited Cu or by electrochemical plating of Pd 2+ . The resulting surfaces appear to consist of three-dimensional Pd-structures of an unknown thickness that we believe to scale with the palladium coverage, θ Pd/Au . This last parameter is inversely proportional to the HOR/HER-activity of the Pd-on-Au surfaces, in agreement with numerous theoretical and experimental studies in acid media that correlate this effect to the tensile strain induced by the Au-substrate on the Pd-lattice. Proton-exchange membrane fuel cells (PEMFCs) fueled with hydrogen stored at 700 bar can attain energy densities in excess of 200 Wh · kg −1 (on a PEMFC system basis), making them excellent candidates for the propulsion of environmentally-benign, full range (≥ 300 miles) vehicles.1 However, the actual commercialization of PEMFC powered cars has been deterred by the lack of a hydrogen infrastructure and the high cost of the PEMFC. In this last respect, a significant fraction of the system's price is related to the costly platinum-based catalysts needed to catalyze the oxidation of hydrogen and the reduction of oxygen taking place at the FC anode and cathode, respectively.1-3 The kinetics of the oxygen reduction reaction (ORR) on Pt 4 are ≈7 orders of magnitude slower than those of the hydrogen oxidation reaction (HOR), 5 in agreement with the HOR 5 -and ORR 4 -exchange-current density (i 0 ) values of 4 ± 2 · 10 +2 mA · cmPt estimated by Neyerlin and coworkers (at 80• C and 100 kPa H 2 /air partial pressure). As such, the Pt-loading at the PEMFC's cathode (≈0.2-0.4 mg Pt · cm −2 ) is well above the ≤ 0.05 mg Pt · cm −2 required for the anodic HOR, and thus much research is being devoted to the development of more active and/or less expensive ORR catalysts.6-10 These include alloys of Pt with non-noble metals like Ni, Co or Cu (as well as their de-alloyed derivatives), and catalysts consisting of non-noble metal nanoparticles covered by one or a few monolayers of Pt (i.e., the so-called "core-shell" catalysts).Alternatively, operating a fuel cell in alkaline environment allows for the use a wider variety of potentially inexpensive, noblemetal free ORR-catalysts. Among these, certain materials based on Fe-, Co-and/or Cu-N 4 chelates (or equivalent no...

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Section: −2supporting

confidence: 89%

Section: −2supporting

confidence: 85%

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Bulk-Palladium and Palladium-on-Gold Electrocatalysts for the Oxidation of Hydrogen in Alkaline Electrolyte

Henning

Herranz

Gasteiger

2014

J. Electrochem. Soc.

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“…The electrocatalytic effect cannot be explained simply in terms of larger dispersion and nanostructuring of palladium particles. By using the relationship concerning equivalency of the charge equal to 405 μC cm −2 to the reduction of PdO monolayer under voltammetric conditions in acid medium [39], we can estimate from the data of Fig. 3 the electrochemically active surface areas characteristic of both catalytic systems: palladium stabilized with N-donor ligands (Fig.…”

Section: −2mentioning

confidence: 99%

Fabrication of Nanostructured Palladium Within Tridentate Schiff-Base-Ligand Coordination Architecture: Enhancement of Electrocatalytic Activity Toward CO2 Electroreduction

et al. 2014

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There has been growing interest in the electrochemical reduction of carbon dioxide (CO 2 ), a potent greenhouse gas and a contributor to global climate change, and its conversion into useful carbon-based fuels or chemicals [1][2][3][4][5]. Numerous homogeneous and heterogeneous catalytic systems have been proposed to induce the CO 2 reduction and, depending on the reaction conditions (applied potential, choice of buffer, its strength and pH, local CO 2 concentration, or the catalyst used) various products that include carbon monoxide, oxalate, formate, carboxylic acids, formaldehyde, acetone, or methanol, as well as such hydrocarbons as methane, ethane, and ethylene, are typically observed at different ratios. These reaction products are of potential importance to energy technology, food research, medical applications, and fabrication of plastic materials.Given the fact that the CO 2 molecule is very stable, its electroreduction processes are characterized by large overpotentials, and they are not energy efficient. To produce highly efficient and selective electrocatalysts, the transitionmetal-based molecular materials are often considered [6][7][8]. The latter systems are capable of driving multi-electron transfers and, in principle, produce highly reduced species. In reality, such multi-electron charge transfer catalysts tend to effectively induce the two-electron reduction of CO 2 to CO rather than yield highly reduced products in large amounts. Metallic copper electrodes are unique in this respect because they can drive multi-electron transfers. Mechanisms of the successful electrochemical reductions of CO 2 to methane and ethylene can be interpreted in terms of complex processes occurring at copper electrodes [9,10]. It is believed that, during electroreduction, the rate limiting step is the protonation of the adsorbed CO product to form the CHO adsorbate [11]. Significant decrease of the reaction overpotentials can be achieved with the use of the metal complex modified electrodes capable of both mediating electron transfers and stabilizing the reduced products [12].Because reduction of CO 2 can effectively occur by hydrogenation [13], in the present work, we concentrate on such a model catalytic system as nanostructured metallic palladium capable of absorbing reactive hydrogen in addition to the ability to adsorb monoatomic hydrogen at the interface [14][15][16]. Under such conditions, the two-electron reduction of CO 2 typically to CO [12] is favored. When the reaction proceeds on palladium in aqueous KHCO 3 solutions, carbon monoxide together with hydrogen and small amounts of formate are produced [17][18][19]. Further, it has been postulated that CO and COOH adsorbates are expected to be formed at the surfaces of Pd electrodes at −1.0 V (vs. Ag/AgCl) and, subsequently, desorbed at even more negative potentials [20].To produce highly dispersed and stabilized palladium nanoparticles (as for Fig. 1a), we have generated them by electrodeposition (through consecutive potential cycling) from the thin film of...

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“…Literature pertaining to the anodic oxidation of Pd is limited (47,69,(73)(74)(75)(76). The stability and reactivity of surface oxides on Pd are highly dependent upon the electrode history.…”

Section: Literature Review a Anodic Electrocatalysis And The Rolmentioning

confidence: 99%

Application of modulated hydrodynamic voltammetry to the study of anodic electrocatalysis

Austin

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Structural changes of surface oxide layers on palladium

Cited by 153 publications

References 31 publications

Bulk-Palladium and Palladium-on-Gold Electrocatalysts for the Oxidation of Hydrogen in Alkaline Electrolyte

Bulk-Palladium and Palladium-on-Gold Electrocatalysts for the Oxidation of Hydrogen in Alkaline Electrolyte

Fabrication of Nanostructured Palladium Within Tridentate Schiff-Base-Ligand Coordination Architecture: Enhancement of Electrocatalytic Activity Toward CO2 Electroreduction

Application of modulated hydrodynamic voltammetry to the study of anodic electrocatalysis

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