Scalable synthesis of nanoporous palladium powders

Robinson, David B.; Fares, Stephen J.; Ong, Markus D.; Arslan, Ilke; Langham, Mary E.; Tran, Kim; Clift, W. Miles

doi:10.1016/j.ijhydene.2009.05.026

Cited by 31 publications

(44 citation statements)

References 32 publications

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“…They can be hundreds of micrometers deep. This pore diameter is much larger than that achievable in carbon [36] or platinum group metals [37,38] but this material's pores have sufficient and consistent aspect ratio to test design principles derived in the previous chapter. In pores smaller than 10 nm, mass transport limitations become severe, especially as effects of finite ion and solvent size become important, [39][40][41][42] so models must be more complicated.…”

Section: Introductionmentioning

confidence: 82%

“…These electrodes can be modeled as arrays of cylindrical pores, each with a capacitance of Table 4-1 presents the predicted number of moles stored per liter of electrode volume per volt as a function of pore radius. Pores in the 1-10 nm range are achievable through various methods, including pyrolysis of templated polymers to form porous carbon electrodes, [96] reduction of metals in surfactant templates, [37,38] and dealloying. [97] These structures are not square arrays of uniform cylindrical pores, and specific adsorption can affect the amount delivered, [98] but this model can still closely capture their behavior.…”

Section: Capacitive Deliverymentioning

confidence: 99%

“…[119,131] A flexible route to bulk quantities of nanoporous metal and semiconductor powders is chemical reduction or precipitation in liquid crystals formed by concentrated aqueous surfactants. [19,37,38] Each of these is a promising substrate for fabrication of a bulk electrostatic supercapacitor, providing high surface area and satisfactory or tunable curvature. A few examples are shown in Figure 6-1.…”

Section: Substrate Conductormentioning

confidence: 99%

“…[117] A simple implementation of a pore hierarchy could be a packed powder of nanoporous particles. [38] An optimal design would most likely involve an ordered arrangement of identical subunits. Such a design would also be easy to model, allowing experimental verification of design principles, and it may provide a useful step toward synthesis of interpenetrated structures.…”

Section: Introductionmentioning

confidence: 99%

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Optimized nanoporous materials.

Langham¹,

Jacobs²,

Ong³

et al. 2009

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Nanoporous materials have maximum practical surface areas for electrical charge storage; every point in an electrode is within a few atoms of an interface at which charge can be stored. Metal-electrolyte interfaces make best use of surface area in porous materials. However, ion transport through long, narrow pores is slow. We seek to understand and optimize the tradeoff between capacity and transport. Modeling and measurements of nanoporous gold electrodes has allowed us to determine design principles, including the fact that these materials can deplete salt from the electrolyte, increasing resistance. We have developed fabrication techniques to demonstrate architectures inspired by these principles that may overcome identified obstacles. A key concept is that electrodes should be as close together as possible; this is likely to involve an interpenetrating pore structure. However, this may prove extremely challenging to fabricate at the finest scales; a hierarchically porous structure can be a worthy compromise.

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Section: Introductionmentioning

confidence: 82%

Section: Capacitive Deliverymentioning

confidence: 99%

Section: Substrate Conductormentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Optimized nanoporous materials.

Langham¹,

Jacobs²,

Ong³

et al. 2009

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“…Such a structure would exhibit rapid mass transport to the pore surface, faster reaction kinetics within the structure, and high capacitance in electrochemical double-layer capacitors. Palladium nanoparticles have been grown with interconnected ~3nm pores using a metal-surfactant paste, and it has been shown that the pore structure and morphology can be controlled by synthesis conditions [2,3]. In order to synthesize porous Pd nanostructures with optimal pore morphology for hydrogen storage, the growth of Pd in the surfactant network must first be understood.…”

mentioning

confidence: 99%

Liquid Stage in-situ Growth of Pd Nanoparticles in a Surfactant Liquid Crystal Template

et al. 2011

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As the global demand and consumption of clean and renewable electrical energy continues to grow, there is a complementary need for efficient energy storage technologies that charge rapidly. Currently, mesoporous metal nanoparticles, particularly Pd, are being examined for potential uses in hydrogen storage, electrochemistry (double-layer capacitors), and catalysis [1]. In all these applications, surface interactions control performance. An ideal structure would have a highlyconnected pore morphology, where any point in the structure is within a few atoms of a surface interface. Such a structure would exhibit rapid mass transport to the pore surface, faster reaction kinetics within the structure, and high capacitance in electrochemical double-layer capacitors. Palladium nanoparticles have been grown with interconnected ~3nm pores using a metal-surfactant paste, and it has been shown that the pore structure and morphology can be controlled by synthesis conditions [2, 3]. In order to synthesize porous Pd nanostructures with optimal pore morphology for hydrogen storage, the growth of Pd in the surfactant network must first be understood.Using in-situ STEM microscopy and a fluid stage by Hummingbird Scientific, the e-beam growth of Pd nanostructures can be recorded with nanometer spatial resolution. The in-situ fluid stage consists of 2 silicon nitride windows, each 50 nm thick. The chips are stacked, being separated by 50-70nm tall gold spacers, providing a channel for the liquid (Pd paste). Here we us this in-situ experimental setup on aqueous Pd salt solutions (control) and Pd-surfactant pastes. Figure 1 shows the progressive growth of Pd nanostructures from the Pd salt solution. Each image is taken ~10 seconds after the preceding image, providing an indication of the growth rate. The Pd growth consists of initial homogeneous nucleation of seed particles, followed by the coarsening and fusing of the small particles to grow large networks. Figure 2 shows the growth of Pd structure within the surfactant support. The initial nucleation of seed particles was not captured, but these images show the agglomeration and fusing of small particles, forming a larger porous Pd network. Diffusion and growth kinetics of Pd in the surfactant paste is much slower than in the aqueous solution. Far less nucleation of seed Pd particles occurs in the surfactant paste. Instead, growth of large networks is more dependent on the motion and agglomeration of existing Pd particles.[1] F.

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Supercapacitive transport of pharmacologic agents using nanoporous gold electrodes

Gittard

Pierson

et al. 2010

Biotechnology Journal

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In this study, nanoporous gold supercapacitors were produced by electrochemical dealloying of gold-silver alloy. Scanning electron microscopy and energy dispersive X-ray spectroscopy confirmed completion of the dealloying process and generation of a porous gold material with approximately 10 nm diameter pores. Cyclic voltammetry and chronoamperometry of the nanoporous gold electrodes indicated that these materials exhibited supercapacitor behavior. The storage capacity of the electrodes measured by chronoamperometry was approximately 3 mC at 200 mV. Electrochemical storage and voltage-controlled delivery of two model pharmacologic agents, benzylammonium and salicylic acid, was demonstrated. These results suggest that capacitance-based storage and delivery of pharmacologic agents may serve as an alternative to conventional drug delivery methods.

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Scalable synthesis of nanoporous palladium powders

Cited by 31 publications

References 32 publications

Optimized nanoporous materials.

Optimized nanoporous materials.

Liquid Stage in-situ Growth of Pd Nanoparticles in a Surfactant Liquid Crystal Template

Supercapacitive transport of pharmacologic agents using nanoporous gold electrodes

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