There is a great interest in the development of advanced hydrogen absorbing materials for hydrogen purification and storage. Palladium has strong potential to play a major role in many aspects of a hydrogen based economy, leading to promising applications, encompassing hydrogen purification, storage, and detection. Here, we report on the synthesis of novel Cd@Pd core/shell nanostructured materials for hydrogen sorption and storage. The effect of a capping agent was investigated, showing that it plays an important role in the formation of the uniform and small size of the Cd@Pd nanostructures. Our study has shown that the capacity for hydrogen sorption and storage depended strongly on the composition and structure of the formed Pd-based nanomaterials, as well as the applied electrode potential. The Cd@Pd core/shell nanostructure with an optimized composition of 1:2 exhibited the highest capacity for hydrogen storage, and a 340% increase was achieved in comparison with pure Pd nanoparticles. In addition, by using Cd as the core, the potentially negative environmental impact due to the toxicity of the Cd species was minimized. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved,

ADVERTISEMENT RETURN TO ISSUEPREVReviewNEXTPalladium-Based Nanomaterials: Synthesis and Electrochemical ApplicationsAicheng Chen* and Cassandra OstromView Author Information Department of Chemistry, Lakehead University, 955 Oliver Road, Thunder Bay, Ontario P7B 5E1, Canada*Phone: 807-343-8318. Fax: 807-346-7775. E-mail: [email protected]Cite this: Chem. Rev. 2015, 115, 21, 11999–12044Publication Date (Web):September 24, 2015Publication History Received30 May 2015Published online24 September 2015Published inissue 11 November 2015https://doi.org/10.1021/acs.chemrev.5b00324Copyright © 2015 American Chemical SocietyRIGHTS & PERMISSIONSACS AuthorChoiceArticle Views34035Altmetric-Citations575LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (51 MB) Get e-AlertsSUBJECTS:Catalysts,Hydrogen,Metal nanoparticles,Nanoparticles,Palladium Get e-Alerts

In view of the inherent limitations of current portable technology energy sources, the implementation of micro fuel cells is becoming increasingly appealing. This has generated great interest in the development of direct formic acid micro fuel cells. In this study, nanoporous Pd and four nanoporous bimetallic Pd-M catalysts with an atomic ratio of 90:10, where M = Cd, Pb, Ir, and Pt, were synthesized via a facile hydrothermal method and examined for the electrochemical oxidation of formic acid. The electrocatalytic activity of these nanoporous electrode materials was studied with the use of linear sweep voltammetry and chronoamperometry. Our chronoamperometric measurements have shown that the initial electrochemical performance of the nanoporous Pd-M electrodes toward formic acid oxidation was almost independent of the alloying materials; however, the second incorporated metal strongly affected the stability of the Pd-based electrocatalysts. The mechanisms of the oxidation of formic acid were further examined with the aid of in situ electrochemical ATR-FTIR spectroscopy. For the nanoporous Pd, PdCd, and PdPb catalysts, oxidation proceeds through the direct mechanism, whereas the indirect mechanism, along with major CO poisoning, was observed in the case of the PdIr and PdPt catalysts. The incorporation of even small amounts of Pt and Ir to Pd was found to inhibit the oxidation of formic acid. On the other hand, the addition of Pb to Pd served to promote the direct mechanism, which in turn makes these Pd-based catalysts both cost and electrocatalytically more effective.

The success of acceptable hydrogen storage capacities on high surface area carbon materials at ambient temperature requires the combination of both physisorption and chemisorption. Despite the sole reliance on physisorption for hydrogen uptake in carbon, the dispersal of transition metal catalysts on carbon materials significantly enhances hydrogen uptake at ambient temperatures, via the process I of hydrogen spillover. In the present study, hydrogen electrosorption onto activated carbon materials modified with different trimetallic dissociation catalysts (Pd-Ag-Cd) was investigated in an acidic medium using using cyclic voltammetry and chronoamperometry. A significant synergistic effect on hydrogen storage was observed, which could be attributed to the electrochemical reduction of hydrogen ions initially at the Pd-based nanoparticles and the hydrogen surface diffusion subsequently to the activated carbon. Utilizing electrochemical methods, the optimized composition of the Pd-Ag-Cd alloys was-determined to be Pd80Ag10Cd10, with the highest hydrogen sorption capacity at a hydrogen desorption charge of 18.49 C/cm(2).mg. With increased kinetics and a decrease in the phase transition, the significant enhancement of hydrogen sorption, in comparison to the Pd-Ag and Pd-Cd bimetallic alloys, was further demonstrated, making Pd-Ag-Cd catalysts attractive for use as hydrogen dissociation catalysts for applications in both hydrogen purification and storage.

The use of hydrogen as an energy carrier is an attractive solution toward addressing global energy issues and reducing the effects of climate change. Design of new materials with high hydrogen sorption capacity and high stability is critical for hydrogen purification and storage. In this study, titanium dioxide nanotubes (TiO2NTs) were modified with palladium nanoparticles (PdNPs) utilizing a facile photo-assisted chemical deposition approach. Electrochemical anodization was employed for the direct growth of TiO2NTs. The PdNP functionalized TiO2NTs (TiO2NT/Pd) were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The hydrogen sorption behaviours and stability of the TiO2NT/Pd nanocomposites were investigated and compared with nanoporous Pd networks that were deposited on a bulk titanium substrate (Ti/Pd) using cyclic voltammetry (CV) and chronoamperometry (CA). Our studies show that the TiO2NT/Pd nanocomposites possess a much higher hydrogen storage capacity, faster kinetics for hydrogen sorption and desorption, and higher stability than the nanoporous Pd.

Recent studies have shown that the use of hydrogen peroxide as a fuel cell oxidant instead of oxygen significantly increases the power density. In this paper, we report on highly active carbon supported PdPt catalysts for hydrogen peroxide reduction. Four different PdPt electrocatalysts, Pd/C, Pt/C, Pd0.5Pt0.5/C, and Pd0.25Pt0.75/C, were prepared and characterized using transmission electron microscopy, energy dispersive x-ray spectroscopy, x-ray diffraction, and Brunauer-Emmet-Teller surface area analysis. The electrocatalytic activities of these synthesized catalysts were studied using a rotating disk electrode system with a combination of linear sweep voltammetry and chronoamperometry. Our studies show that the Pd0.25Pt0.75/C catalyst has the highest activity for hydrogen peroxide reduction, outperforming the Pd/C, Pt/C, and Pd0.5Pt0.5/C catalysts. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3548529] All rights reserved.

High surface area carbon materials are promising for low-temperature storage of hydrogen by physisorption. To achieve acceptable hydrogen capacities at ambient temperature, chemisorption must come into play. The dispersion of transition metal catalysts to carbon materials can enhance the ambient temperature adsorption capacity of the carbon materials via the hydrogen spillover mechanism. In this study, three different hydrogen dissociation catalysts (Pd, PdAg, and PdCd nanoparticles) were dispersed onto surfaces of activated carbon. The surface composition of these metal-dispersed carbon materials was analyzed using X-ray photoelectron spectroscopy (XPS) and the specific surface areas, and pore sizes were measured using N-2 adsorption/desorption. The effect of the dispersed catalysts on the hydrogen adsorption properties of the activated carbon was systemically investigated at 77 K and room temperature (295 K) using a volumetric gas adsorption technique. At 77 K, the catalysts have no effect, and the hydrogen capacity of the materials is strictly related to the specific surface area. At room temperature, hydrogen spillover was observed from the catalysts to the carbon material. The hydrogen capacity is related to the adsorption strength of hydrogen atoms to the catalyst particle surface atoms, which was verified with DFT calculations. In addition, this study reveals that the PdCd nanoparticle possesses much higher hydrogen spillover enhancement (108%) than the pure Pd and PdAg nanoparticles, promising for hydrogen storage.

Hydrogen-absorbing materials are crucial for both the purification and storage of hydrogen. Pd and Pd-based alloys have been studied extensively for their use as both hydrogen dissociation catalysts and hydrogen selective membrane materials. It is known that incorporating metal atoms of different sizes into the Pd lattice has a major impact on the hydrogen absorption process. In this paper, hydrogen electrosorption into nanostructured Pd-Cd alloys has been studied for different compositions of Cd that varied from 0 to 15 at. %. The low cost of Cd makes it an attractive material to combine with Pd for hydrogen sorption. A combination of chronoamperometry and cyclic voltammetric experiments was used to determine the ratio of the H/(Pd + Cd) and the kinetics of hydrogen sorption into these Pd-Cd alloys at different potentials. It was found that the maximum H/(Pd + Cd) value was 0.66 for pure Pd, and this decreased with increasing the amount of Cd. Also, the alpha (solid solution) to beta phase (metal hydride) hydrogen transition was determined to be the slowest step in the absorption process and was practically eliminated when an optimum amount of Cd atoms was doped (i.e., Pd-Cd(15%)). With increasing the amount of Cd, more hydrogen was absorbed into the Pd-Cd nanostructures at the higher potentials (the alpha phase region). The faster kinetics, along with the decrease in the phase transition of hydrogen sorption into the Pd-Cd nanostructures when compared to pure Pd, makes the Pd-Cd nanostructures attractive for use as a hydrogen dissociation catalytic capping layer for other metal hydrides or as a hydrogen selective membrane.