Size Effects in Monolayer Catalysis—Model Study: Pt Submonolayers on Au(111)

Bae, Sang-Eun; Gökcen, Dinçer; Liu, Ping; Mohammadi, P.; Brankovic, Stanko R.

doi:10.1007/s12678-012-0082-5

Cited by 49 publications

(72 citation statements)

References 40 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Also, the presence of a single monolayer of the most active catalyst components raises issues of stability (although no long-term performance deterioration has been reported [80,93] underlying metals of the core, either via geometric or ligand effects [143,144]. For sub-monolayers and nanoclusters, finite size effects have also to be taken into account due to the different strain exerted by the substrate to small particles from that to continuous films; in this way the electronic properties and catalytic activity modification can also be correlated to particle size [145][146][147]. Adzic and co-workers have systematically explored these effects and reported some of the highest Pt utilization values for oxygen reduction and alcohol oxidation (see, for example, [64][65][66]94,95]) while also finely tuning the shell properties by using multi-metallic cores that contain apart from a second noble metal M ' noble other noble or less noble metals M (see, for example, [87,93,96]).…”

Section: Characteristics Of the Two Galvanic Replacement Approaches Fmentioning

confidence: 99%

Electrocatalysts Prepared by Galvanic Replacement

et al. 2017

View full text Add to dashboard Cite

Galvanic replacement is the spontaneous replacement of surface layers of a metal, M, by a more noble metal, M noble , when the former is treated with a solution containing the latter in ionic form, according to the general replacement reaction: nM + mM noble n+ → nM m+ + mM noble. The reaction is driven by the difference in the equilibrium potential of the two metal/metal ion redox couples and, to avoid parasitic cathodic processes such as oxygen reduction and (in some cases) hydrogen evolution too, both oxygen levels and the pH must be optimized. The resulting bimetallic material can in principle have a M noble-rich shell and M-rich core (denoted as M noble (M)) leading to a possible decrease in noble metal loading and the modification of its properties by the underlying metal M. This paper reviews a number of bimetallic or ternary electrocatalytic materials prepared by galvanic replacement for fuel cell, electrolysis and electrosynthesis reactions. These include oxygen reduction, methanol, formic acid and ethanol oxidation, hydrogen evolution and oxidation, oxygen evolution, borohydride oxidation, and halide reduction. Methods for depositing the precursor metal M on the support material (electrodeposition, electroless deposition, photodeposition) as well as the various options for the support are also reviewed. 1. Principle of Galvanic Replacement/Deposition 1.1. Thermodynamic Considerations When a metal, M (e.g., Cu, Fe, Co, Ni, Al, etc.), is immersed in a solution containing ions of a more noble metal, M noble n+ (e.g., Pt, Au, Pd, Ag, Ru, Ir, Rh, Os, etc.-i.e., a metal with a higher standard potential) then, due to the difference in their standard electrochemical potentials, E 0 noble − E 0 > 0, and provided that the ionic form of M is stable under the given experimental conditions (of temperatue, pH, complexing agents etc.), the following reaction is thermodynamically favored and can take place spontaneously: M noble n+ + n/m M → M noble + n/m M m+ (1) This reaction, which bears similarities with transmetalation reactions between metal complexes [1] and is also known as immersion plating [2] in the plating industry and galvanic replacement [3] in materials chemistry, can be considered to originate from the coupling of the following two half-reactions: M noble n+ + ne − ↔ M noble (E 0 noble) (2) M m+ + me − ↔ M (E 0) (3)

show abstract

Section: Characteristics Of the Two Galvanic Replacement Approaches Fmentioning

confidence: 99%

Electrocatalysts Prepared by Galvanic Replacement

et al. 2017

View full text Add to dashboard Cite

show abstract

“…[11][12][13][14][15][16] On the other hand, the morphology of P deposit is a direct function of SLRR reaction kinetics and stoichiometry. 12,17 They are dependent on experimental conditions.…”

Section: Deposition Via Surface Limited Redox Replacement (Slrr) Of Umentioning

confidence: 99%

Editors' Choice—Reaction Kinetics of Metal Deposition via Surface Limited Redox Replacement of Underpotentially Deposited Monolayer Studied by Surface Reflectivity and Open Circuit Potential Measurements

Bulut

Dole

et al. 2017

J. Electrochem. Soc.

Self Cite

View full text Add to dashboard Cite

Presented work studies the relation between kinetics of metal deposition via surface limited redox replacement (SLRR) of underpotentially deposited (UPD) monolayer (ML) and experimental parameters of reaction solution such as meal ions concentrations and supporting electrolyte concentration. The model system is Au deposition on Au(111) via SLRR of Pb UPD ML. The rate constant of the SLRR reaction for different solution designs is determined from temporal change of electrode surface reflectivity and from the open circuit potential transients' analysis. The obtained results show clearly that reaction kinetics of metal deposition via SLRR of UPD ML is significantly affected by the design of the reaction solution i.e. the UPD metal ion, depositing metal ion, and supporting electrolyte concentrations. The ten-fold change of concentration of either solution parameter produces approximately the same change in the value of the rate constants. The presented results have fundamental importance for the future development and application of the metal deposition via SLRR of UPD ML. They offer a link between the reaction solution design and expected trend in SLRR reaction rate, which transposes to successful control of deposition flux, nucleation density and resulting morphology of the deposit. Deposition via Surface Limited Redox Replacement (SLRR) of underpotentially deposited (UPD) monolayer (ML)1 has gained a lot of attention and applications in last two decades.2-4 The main idea is to use an UPD ML as sacrificial material to reduce/deposit a more noble metal (SLRR reaction i.e. galvanic displacement). The basic stoichiometry of the SLRR reaction and deposition process is shown by Equation 1.Here, M and P and S(h,k,l) stand for UPD metal/ion, depositing metal/ion and substrate, while m + /m and p + /p represent the oxidation state of M and P metal ions and corresponding stoichiometry coefficients. Over the years, several experimental protocols for deposition via SLRR of UPD ML have been developed. The first and the basic one, 1,6 involves formation of the UPD ML of M on the substrate S(h,k,l), (potential controlled step) and then subsequent immersion of M UPD /S(h,k,l) into a separate reaction solution where SLRR occurs and deposition of P takes place at open circuit (sample shuffling approach). The second protocol involves the stagnant substrate but sequential application of potential control in solution for UPD ML formation and then application of solution for SLRR reaction and deposition of P at open circuit (solution shuffling approach 7 ). The most recent development has introduced a "one-solution, one-cell" experimental design. 8,9 In this case, the same solution serves for UPD ML formation and subsequent SLRR reaction at open circuit potential. This protocol assumes a sequence of potential controlled step, where co-deposition of UPD ML of M with small amount of P occurs, and the open circuit step, where SLRR reaction and deposition of P proceeds. The very details of these three protocols and their applications hav...

show abstract

“…The coverage and morphology of the deposited metal P can be determined experimentally using well-established surface area characterization techniques, for example, temperature programmed desorption or electrochemical adsorption [17]. Alternatively, other methods such as STM or AFM can be used [52,54]. The overall stoichiometry of the SLRR reaction and deposition process is also dependent on specific experimental conditions favoring a certain oxidation state of the metal constituting the UPD layer.…”

Section: Stoichiometry Of Slrr Reactions and Deposition Processmentioning

confidence: 99%

“…This observation is in agreement with the previous discussion regarding the effect of SLRR stoichiometry coefficients on nucleation rate, that is, SLRR reactions with higher m/p ratio yield higher nucleation rates and smaller stable nuclei. The example in Figure 3.6 demonstrates that manipulation of the experimental conditions for SLRR reactions gives the opportunity to design and synthesize catalyst monolayers with different morphology, cluster size, and coverage [44,54,22].…”

Section: Driving Force For Slrr Reaction and Nucleation Rate Of Deposmentioning

confidence: 99%

See 1 more Smart Citation

Electrochemical Surface Processes and Opportunities for Material Synthesis

Brankovic¹,

Zangari²

2015

Advances in Electrochemical Sciences and Engineering

Self Cite

View full text Add to dashboard Cite

Technological advances in the operation and performance of microelectronic, optical, magnetic, and, more recently, energy conversion devices depend in large part on an ever-increasing accuracy of material synthesis and film fabrication methods. In particular, the ongoing miniaturization of devices requires strict control of the crystal structure and microstructure in film as well as patterned structures, often down to the atomic scale.Electrodeposition has an important role to play in this pursuit toward miniaturization and enhanced performance [1]. Underpotential deposition (UPD) [2, 3] and surface-limited redox replacement (SLRR) [4] exploit the low energy of the metal ion precursors in solution (of the order of the thermal energy, 0.025-0.03 eV) to control the formation or replacement of single atomic layers via self-limiting processes. In UPD, a monoatomic layer of metal M is deposited on a conductive substrate S at a potential more positive than the redox potential of M [2]. This shift in redox potential is made possible by the fact that the M-S bond is stronger than the M-M bond; since the effective pair interaction V eff = V MM + V SS − 2V MS is typically in the order of 0.01-0.1 eV, only low energy precursors are sensitive to these energy differences, thus limiting the deposit to one (or sometimes two) atomic layers. SLRR involves UPD monolayer formation, followed by displacement of this layer with a full or partial monolayer of a more noble element, through a cementation process [4]. An analogous process, selective electrodesorption-based atomic layer deposition (SEBALD) consists in the formation at UPD of a sacrificial sulfur monolayer to induce UPD of late transition metals such as Fe, Co, and Ni in the form of monolayers or nanosized islands [5].Underpotential codeposition (UPCD) is a generalization of the UPD process, whereby alloy electrodeposition occurs at potentials more positive than the redox potential of the less noble element [6]. UPCD is made possible by the effective atomic pair interactions in the solid state, or equivalently by the alloying bond enthalpy. In contrast with UPD, UPCD is used to form alloy films of arbitrary

show abstract

Size Effects in Monolayer Catalysis—Model Study: Pt Submonolayers on Au(111)

Cited by 49 publications

References 40 publications

Electrocatalysts Prepared by Galvanic Replacement

Electrocatalysts Prepared by Galvanic Replacement

Editors' Choice—Reaction Kinetics of Metal Deposition via Surface Limited Redox Replacement of Underpotentially Deposited Monolayer Studied by Surface Reflectivity and Open Circuit Potential Measurements

Electrochemical Surface Processes and Opportunities for Material Synthesis

Contact Info

Product

Resources

About