Scanning Electrochemical Microscopy of Redox-Mediated Hydrogen Evolution Catalyzed by Two-Dimensional Assemblies of Palladium Nanoparticles

Li, Fēi; Ciani, Ilenia; Bertoncello, Paolo; Unwin, Patrick R.; Zhao, Jianjun; Bradbury, Christopher R.; Fermı́n, David J.

doi:10.1021/jp8001228

Cited by 49 publications

(39 citation statements)

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“…Depending on the nature of the electrochemical reaction, the current is measured at the UME or at the substrate electrode. [226,227] A particularly interesting method of model electrocatalyst screening has been reported by the research group of Hayden. [220] Many recent reports have appeared in which SECM was applied to assess a range of different material combinations for fuel-cell reactions, [221][222][223][224] as has been summarized in recent reviews.…”

Section: High-throughput Electrocatalyst Screeningmentioning

confidence: 99%

“…The approach has been used to study the HER at well-defined arrays of NPs in different environments. [226,227] A particularly interesting method of model electrocatalyst screening has been reported by the research group of Hayden. [228] A masked substrate was used in an ultrahigh vacuum physical vapor deposition (PVD) chamber to deposit a range of different particle sizes in an array.…”

Section: High-throughput Electrocatalyst Screeningmentioning

confidence: 99%

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Electrochemistry of Nanoparticles

et al. 2014

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Metal nanoparticles (NPs) find widespread application as a result of their unique physical and chemical properties. NPs have generated considerable interest in catalysis and electrocatalysis, where they provide a high surface area to mass ratio and can be tailored to promote particular reaction pathways. The activity of NPs can be analyzed especially well using electrochemistry, which probes interfacial chemistry directly. In this Review, we discuss key issues related to the electrochemistry of NPs. We highlight model studies that demonstrate exceptional control over the NP shape and size, or mass-transport conditions, which can provide key insights into the behavior of ensembles of NPs. Particular focus is on the challenge of ultimately measuring reactions at individual NPs, and relating the response to their structure, which is leading to imaginative experiments that have an impact on electrochemistry in general as well as broader surface and colloid science.

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Section: High-throughput Electrocatalyst Screeningmentioning

confidence: 99%

Section: High-throughput Electrocatalyst Screeningmentioning

confidence: 99%

Electrochemistry of Nanoparticles

et al. 2014

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“…As such the use of Pd NPs was highly encouraged towards HER. 8,9 However, as compared to Pt, Pd displayed less electrocatalytic performance towards HER. Thus, modification of the surface properties coupled with metal alloying are necessary to improve the electrocatalytic properties of Pd NPs.…”

Section: Introductionmentioning

confidence: 99%

Reduced graphene oxide nanosheets decorated with Au, Pd and Au–Pd bimetallic nanoparticles as highly efficient catalysts for electrochemical hydrogen generation

et al. 2015

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Reduced graphene oxide (rGO) nanosheets decorated with gold nanoparticles (Au NPs/rGO), palladium nanoparticles (Pd NPs/rGO), and gold-palladium bimetallic nanoparticles (Au-Pd NPs)/rGO are synthesized by a simple solution chemistry approach using ascorbic acid as ecofriendly reducing agent. These materials are characterized by high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). The as-prepared nanocomposites are tested as electrocatalysts for efficient hydrogen evolution in deaerated 0.5 M H 2 SO 4 aqueous solution using polarization and impedance measurements. Experimental findings show that the tested catalysts exhibit fast hydrogen evolution kinetics with onset potentials as low as −17, −7.2, and −0.8 mV vs. RHE for Au NPs/rGO, Pd NPs/rGO, and Au-Pd NPs/rGO, respectively. In addition, Tafel slopes of 39.2, 33.7 and 29.0 mV dec -1 and exchange current densities of 0.09, 0.11, and 0.47 mA cm -2 are measured for Au NPs/rGO, Pd NPs/rGO, and Au-Pd NPs/rGO, respectively. The tested materials not only maintain their high performance after 5000 sweep cycles, but their activity is simultaneously enhanced after this aging process. These findings reveal that the tested catalysts, particularly Au-Pd NPs/rGO, are promising candidates among other noble metal catalysts for hydrogen evolution, approaching the commercial Pt/C catalyst (onset potential: 0.0 mV, Tafel slope: 31 mV dec -1 , and exchange currrent density: 0.78 mA cm -2 ). The high hydrogen evolution reaction (HER) activity of such materials is likely due to the abundance of active catalytic sites, the increased electrochemically accessible surface area and significantly improved electrochemical conductivity.

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“…This is particularly true in the area of heterogeneous catalysis (1)(2)(3)(4)(5)(6)(7)(8)(9)(10). The advantages of ensembles of nanoparticles over foils of the same catalytic material, as well as the role of the particle size, have been frequently recognized with regard to rates.…”

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Catalysis at the nanoscale may change selectivity

Costentin

Savéant

2016

Proc. Natl. Acad. Sci. U.S.A.

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Among the many virtues ascribed to catalytic nanoparticles, the prospect that the passage from the macro-to the nanoscale may change product selectivity attracts increasing attention. To date, why such effects may exist lacks explanation. Guided by recent experimental reports, we propose that the effects may result from the coupling between the chemical steps in which the reactant, intermediates, and products are involved and transport of these species toward the catalytic surface. Considering as a thought experiment the competitive formation of hydrogen and formate upon reduction of hydrogenocarbonate ions on metals like palladium or platinum, a model is developed that allows one to identify the governing parameters and predict the effect of nanoscaling on selectivity. The model leads to a master equation relating product selectivity and thickness of the diffusion layer. The latter parameter varies considerably upon passing from the macro-to the nanoscale, thus predicting considerable variations of product selectivity. These are subtle effects in the sense that the same mechanism might exhibit a reverse variation of the selectivity if the set of parameter values were different. An expression is given that allows one to predict the direction of the effect. There has been a tendency to assign the catalytic effects of nanoscaling to chemical reactivity changes of the active surface. Such factors might be important in some circumstances. We, however, insist on the likely role of short-distance transport on product selectivity, which could have been thought, at first sight, as the exclusive domain of chemical factors.energy | nanoparticles | electrocatalysis N anoparticles work wonders in many fields of science and technology. This is particularly true in the area of heterogeneous catalysis (1-10). The advantages of ensembles of nanoparticles over foils of the same catalytic material, as well as the role of the particle size, have been frequently recognized with regard to rates. The answer is more elusive as to the possible effect of nanoscaling on product selectivity. It is tempting to attribute such effects to the creation of surface defects that may be triggered by the deposition of the nanoparticles. We, however, explore another type of rationale.The systems where some relevant information is available are few but concern important processes in the area of contemporary energy challenges (11)(12)(13)(14), namely the electrochemical hydridation of CO 2 into HCO 2 − versus H 2 evolution at a metal electrode in aqueous media (15)(16)(17)(18)(19). This is the case when the metal is palladium with which little formate, if any, is generated upon electrolysis on a Pd foil (18,20), whereas the formate faradaic yield reaches 90-95% with ∼5-nm-diameter Pd nanoparticles dispersed on ∼100-nm carbon particles (18). Very high faradaic yields of formate are similarly found on carbon supported Pt-Pd nanoparticle electrodes in a pH 6.7 phosphate buffer (21,22).How can such major differences in product selectivity be explained whe...

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Scanning Electrochemical Microscopy of Redox-Mediated Hydrogen Evolution Catalyzed by Two-Dimensional Assemblies of Palladium Nanoparticles

Cited by 49 publications

References 67 publications

Electrochemistry of Nanoparticles

Electrochemistry of Nanoparticles

Reduced graphene oxide nanosheets decorated with Au, Pd and Au–Pd bimetallic nanoparticles as highly efficient catalysts for electrochemical hydrogen generation

Catalysis at the nanoscale may change selectivity

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