The effects of soil type and chemical treatment on nickel speciation in refinery enriched soils: A multi-technique investigation

McNear, David H.; Chaney, Rufus L.; Sparks, Donald L.

doi:10.1016/j.gca.2007.02.006

Cited by 83 publications

(60 citation statements)

References 53 publications

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“…30 The X-ray absorption near edge structure (XANES) region within ±30 eV of the absorption edge reveals significant differences among the Pt-Ni aerogels (see Fig. 2A).…”

Section: Resultsmentioning

confidence: 99%

Pt-Ni Aerogels as Unsupported Electrocatalysts for the Oxygen Reduction Reaction

Henning

Kühn

Herranz

et al. 2016

J. Electrochem. Soc.

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The commercial feasibility of polymer electrolyte fuel cells (PEFCs) passes by the development of Pt-based, O 2 -reduction catalysts with greater activities and/or lower Pt-contents, as well as an improved stability. In an effort to tackle these requirements, unsupported bimetallic Pt-Ni nanoparticles (NPs) interconnected in the shape of nanochain networks (aerogels) were synthesized using a simple one-step reduction and gel formation process in aqueous solution. The products of this novel synthetic route were characterized by X-ray absorption spectroscopy to elucidate the materials' structure. Using electrochemical experiments, we probed the surface composition of the as-synthesized aerogels and of equivalent materials exposed to acid, and concluded that a Ni-(hydr)oxide side phase is present in the aerogel with a larger Ni-concentration. Regardless of this initial surface composition, the Pt-Ni aerogels feature a ≈3-fold increase of surface-specific ORR activity when compared to a commercial platinum-on-carbon catalyst, reaching the mass-specific requirement for application in automotive PEFCs. 1 to account for the large overpotential of the oxygen reduction reaction (ORR). Thus, Pt contributes significantly to the fuel cell system cost, and progress to reduce its loading is crucial to meet the long-term PEFC cost target of 40 $/kW set by the U. S. Department of Energy (DOE).2 One approach to reduce this excessive Pt-loading relies on increasing the catalysts' ORR activity, e.g. by alloying platinum with other metals like Ni, Cu and Co, to form materials which show up to one order of magnitude higher mass-specific activity than commercial Pt/C catalysts.3 On the other hand, these carbon-supported materials suffer from significant carbonand Pt-corrosion during the standard operation of PEFCs, gradually compromising their efficiency and reliability. 4 To partially overcome stability issues, research focuses on unsupported materials (e.g. Ptcoated Ni, Co or Cu nanowires 5-7 ) besides extended metal surfaces (e.g. 3 M nanostructured thin film catalysts 8 ) or alternative supports (e.g. conductive metal oxides 9-12 ). Naturally, those materials should be processable into catalytic layer architectures that provide reactant and product diffusion pathways similar to those in conventional Pt/C electrodes to guarantee high catalyst utilization and PEFC performance. 13To meet the requirements mentioned above, un-supported bimetallic electrocatalysts with high surface area (up to ≈80 m 2 /g metal ) and nanochain network structure, referred to as aerogels, have been synthesized. [14][15][16] The synthetic routes to prepare such materials vary, but generally involve the use of stabilizing surfactants and/or organic solvents [17][18][19] that can poison the catalyst's surface and decrease its activity. In contrast to those approaches, our groups have developed a facile one-step synthesis for mono-and bimetallic aerogels based on the reduction of metal salts by NaBH 4 in aqueous solution without addition of stabilizing surfac...

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“…30 The X-ray absorption near edge structure (XANES) region within ±30 eV of the absorption edge reveals significant differences among the Pt-Ni aerogels (see Fig. 2A).…”

Section: Resultsmentioning

confidence: 99%

Pt-Ni Aerogels as Unsupported Electrocatalysts for the Oxygen Reduction Reaction

Henning

Kühn

Herranz

et al. 2016

J. Electrochem. Soc.

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“…However, due to the small size and shallow rooting of these plants, it is probably not correct to invoke a real "metal cycle", that is, an increase of the top soil metal concentration due to the foliar hyperaccumulation of deep-soil metals and subsequent leaf fall. Also, the ability of hyperaccumulators to mobilize more nickel or zinc from soils or rocks does not seem to be higher than in normal plants (Bernal et al 1994;McNear et al 2007;Puschenreiter et al 2005;Shallari et al 2001). A possible hypothesis for the presence of highly tolerant bacteria near the roots of metal hyperaccumulators could be related to the specific tropism, shown in controlled experiments, of roots of hyperaccumulating plants toward soil patches rich in metals, a phenomenon known as "root metal foraging" (Haines 2002;Liu et al 2009;Schwartz et al 1999;Whiting et al 2000).…”

Section: Bacterial Communities In Serpentine Soilmentioning

confidence: 99%

Plants as extreme environments? Ni-resistant bacteria and Ni-hyperaccumulators of serpentine flora

2009

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During recent years there has been an increasing interest in the bacterial communities occurring in unusual, often extreme, environments. On serpentine outcrops around the world, a high diversity of plant species showing the peculiar features of metal hyperaccumulation is present. These metal hyperaccumulators have received much attention for their potential biotechnological exploitation in phytoremediation processes, but also as unusual, extreme habitats for the associated bacterial flora, which could reveal novel details concerning bacterial adaptation. This paper will briefly focus on the research topics that have been addressed to date on bacteria associated with serpentine plants and aims to provide a state of the art and to present possible future directions for research which could lead to new insights on microbial adaptation and evolution, and potentially applied in technologies for sustainable use and remediation of contaminated land.

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“…Several groups have reported that Ni in serpentine soils was associated with the Fe and Mn oxides or silicates [47,48]. In smelter contaminated soils, Ni was associated with organic matter, Fe oxides, as the Ni-Al layered double hydroxide, and as NiO [49]. NiO has very slow dissolution kinetics [50]; the half-time for NiO dissolution at pH 7 is 20 years.…”

Section: Phytomining Soil Nickelmentioning

confidence: 99%

Phytoremediation of Soil Trace Elements

Chaney

Broadhurst

Centofanti

2010

Trace Elements in Soils

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The effects of soil type and chemical treatment on nickel speciation in refinery enriched soils: A multi-technique investigation

Cited by 83 publications

References 53 publications

Pt-Ni Aerogels as Unsupported Electrocatalysts for the Oxygen Reduction Reaction

Pt-Ni Aerogels as Unsupported Electrocatalysts for the Oxygen Reduction Reaction

Plants as extreme environments? Ni-resistant bacteria and Ni-hyperaccumulators of serpentine flora

Phytoremediation of Soil Trace Elements

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