Struktur und eigenschaften von Raney-Nickel-katalysatoren mit zulegierungen für alkalische brennstoffzellen

Ewe, H.; Justi, E.; Schmitt, Alexander

doi:10.1016/0013-4686(74)85025-5

Cited by 24 publications

(4 citation statements)

References 5 publications

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“…One can distinguish several groups of catalytic materials having metallic nickel as the main component. Among them, there are metal-doped-sponge Raney nickel catalysts, − electrochemically deposited bulk double- and ternary-metal catalysts, highly dispersed supported Ni-based catalysts, and single-crystal Ni facets . The first group, Raney nickel catalysts, is the most popular, with the highest number of studies, because of its popularity in liquid electrolyte (KOH)-based alkaline fuel cells.…”

Section: Hor Electrocatalystsmentioning

confidence: 99%

“…However, the catalytic activity and stability of Raney Ni alone as a base metal for this reaction is limited . These problems have been partially overcome by doping of transition metals, such as Ti, ,, La, Cr, Fe, Co, ,, Cu (mostly as a conducting additive), and Mo, , into the Ni–Al alloy at loadings of a few percent prior to extraction by KOH. The resultant Raney nickel catalysts are pyrophoric because of the H 2 evolution during Al leaching and therefore must be handled accordingly, as the nickel is loaded with 0.5–1.2 hydrogen atoms per nickel atom.…”

Section: Hor Electrocatalystsmentioning

confidence: 99%

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Electrocatalysts for Hydrogen Oxidation Reaction in Alkaline Electrolytes

et al. 2018

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In the past 5 years, advances in anionconductive membranes have opened the door for the development of advanced anion-exchange membrane fuel cells (AEMFCs) as the next generation of affordable fuel cells. Several recent works have shown that AEMFCs currently achieve nearly identical beginning-of-life performance as stateof-the-art proton exchange membrane fuel cells. However, until now, these high AEMFC performances have been reached with platinum-group metal (PGM)-based anode and cathode catalysts. In order to fulfill the potential of AEMFCs, such catalysts should in the near future be free of PGMs and, eventually, free of critical raw materials. Although great progress has been achieved in the development of PGM-free catalysts for the oxygen reduction reaction in basic media, significantly less attention has been paid to the catalysis of the hydrogen oxidation reaction (HOR). The much lower HOR activity of Pt in basic media compared with that in acid was itself revealed only relatively recently. While several PGM-based composite materials have shown improved HOR activity in basic media, the HOR kinetics remains slower than necessary for an ideal nonpolarizable electrode. In addition, attempts to move away from PGMs have hitherto resulted in high anode overpotentials, significantly reducing the performance of PGM-free AEMFCs. This would be a major barrier for the large-scale deployment of this technology once the other technological hurdles (e.g., membrane stability) have been overcome. A fundamental understanding of the HOR mechanism in basic media and of the main energy barriers needs to be firmly established to overcome this challenge. This review presents the current understanding of the HOR electrocatalysis in basic media and critically discusses the most recent material approaches. Promising future research directions in the development of the HOR electrocatalysts for alkaline electrolytes are also outlined.

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Section: Hor Electrocatalystsmentioning

confidence: 99%

Section: Hor Electrocatalystsmentioning

confidence: 99%

Electrocatalysts for Hydrogen Oxidation Reaction in Alkaline Electrolytes

et al. 2018

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“…Mechanism in Supported Electrodes The catalyst powder obtained from Raney alloy has a BET surface area of about 70 m 2 9 g-1 (12), A mean pore radius r9 of 1.6" 10 -7 cm is found in catalyst particles having a volume porosity p of 34%. Hence it can be estimated that there are about 107 pore mouths at the outer surface of a catalyst grain having a radius of rk = 10 -3 cm.…”

Section: Description Of the Catalyst Particle And The Reactionmentioning

confidence: 99%

Titanium‐Containing Raney Nickel Catalyst for Hydrogen Electrodes in Alkaline Fuel Cell Systems

Mund

Richter

Sturm

1977

J. Electrochem. Soc.

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In alkaline hydrogen-oxygen fuel cells Raney nickel is employed as catalyst for hydrogen electrodes. The rate of anodic hydrogen conversion has been increased significantly by using a titanium-containing Raney nickel. The properties of the catalyst powder, the influence of particle diameter, and the behavior of electrodes under load are described. Impedance measurements have been used to characterize the electrodes. In fuel cell systems the supported electrodes are normally operated at current densities up to 0.4 A'cm-2; the overload current density of 1 A.cm -~ can be maintained for several hours.The economic factors of the H2-O2 fuel cell are determined essentially by the costs of the catalysts employed in the electrodes. Hence it is rational for commercial applications to avoid the expensive and rare materials such as noble metals. In alkaline electrolyte, the metals nickel and silver are suitable as catalysts for the anode and the cathode, respectively (1, 2). Catalyst powder with large interior surface is used to have a large reactive surface area available. Raney nickel has thus proved useful for the H2 electrode (2) and it is considered in detail. The active material can be depyrophorized by a slow surface oxidation and the catalytic activity could be increased by annealing at 300~ in hydrogen atmosphere (3). The attainable current density of the electrodes depends strongly on the pretreatment of Raney nickel (2, 4).A further increment in catalytic activity could be achieved by changing from a binary Raney alloy to a ternary system in which an additional metal such as iron, molybdenum, or titanium has been alloyed to nickel and aluminum (5-7). The objective of the alloy additives is to produce ternary phases in which Ni, A1, and the additive metal are distributed homogeneously. Only such phases yield homogeneous alloy catalysts with highest activity. The additive metals lead to a lower filling of d bands and to lattice defects.The properties of titanium-containing Raney nickel catalyst are reported here. ExperimentalPreparation of the cataIyst.~The Raney alloy has a mass fraction of 50% A1; the rest consists of Ni and Ti in which the titanium content can be varied from 0 to 5%. When the liquid alloy is quenched in a water bath titanium remains dissolved in the two compounds NiA13 and Ni2Ala. A granulate is formed which can be powdered easily in a mill. Powder with a particle diameter of less than 50 ~m is employed.Aluminum is extracted to an extent of 95% in 6M potassium hydroxide at 80~ titanium remains completely in the catalyst. After washing, the powder is dried in vacuum and subjected to surface oxidation by

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“…Until now, Ni-based materials remain the only alternative to PGMs toward hydrogen electrooxidation, though they are still far from being competitive with Pt. 15,15,19−21,21−24 The early period of Ni-based electrocatalysts for the hydrogen-oxidation reaction (HOR) was associated with Raney Ni, doped with transition metals 25 and with the characteristic particle sizes of a few micrometers. The main drawbacks of Raney Ni lie in the unpredictable deactivation during the aging and the difficulty in handling due to the necessity of keeping pyrophoric solids wet or passivated.…”

Section: ■ Introductionmentioning

confidence: 99%

Effect of the Synthetic Method on the Properties of Ni-Based Hydrogen Oxidation Catalysts

Davydova

Manikandan

Dekel

et al. 2021

ACS Appl. Energy Mater.

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The latest progress in alkaline anion-exchange membranes has led to the expectation that less costly catalysts than those of the platinum-group metals may be used in anion-exchange membrane fuel cell devices. In this work, we compare structural properties and the catalytic activity for the hydrogen-oxidation reaction (HOR) for carbon-supported nanoparticles of Ni, Ni 3 Co, Ni 3 Cu, and Ni 3 Fe, synthesized by chemical and solvothermal reduction of metal precursors. The catalysts are well dispersed on the carbon support, with particle diameter in the order of 10 nm, and covered by a layer of oxides and hydroxides. The activity for the HOR was assessed by voltammetry in hydrogen-saturated aqueous solutions of 0.1 mol dm –1 KOH. A substantial activation by potential cycling of the pristine catalysts synthesized by solvothermal reduction is necessary before these become active for the HOR; in situ Raman spectroscopy shows that after activation the surface of the Ni/C, Ni 3 Fe, and Ni 3 Co catalysts is fully reduced at 0 V, whereas the surface of the Ni 3 Cu catalyst is not. The activation procedure had a smaller but negative impact on the catalysts synthesized by chemical reduction. After activation, the exchange-current densities normalized with respect to the ECSA (electrochemically active surface area) were approximately independent of composition but relatively high compared to catalysts of larger particle diameter.

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Struktur und eigenschaften von Raney-Nickel-katalysatoren mit zulegierungen für alkalische brennstoffzellen

Cited by 24 publications

References 5 publications

Electrocatalysts for Hydrogen Oxidation Reaction in Alkaline Electrolytes

Electrocatalysts for Hydrogen Oxidation Reaction in Alkaline Electrolytes

Titanium‐Containing Raney Nickel Catalyst for Hydrogen Electrodes in Alkaline Fuel Cell Systems

Effect of the Synthetic Method on the Properties of Ni-Based Hydrogen Oxidation Catalysts

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