The electrochemical behaviour of tungsten—I. The dissolution of tungsten and tungsten oxides in buffer solutions

Heumann, Th.; Stolica, N.

doi:10.1016/0013-4686(71)85175-7

Cited by 27 publications

(16 citation statements)

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“…The photocurrent density is also shown to be stable for at least 5 h under continuous illustration (see the Figure S7). These observations are in sharp contrast to WO 3 , which is known to be unstable in neutral electrolytes even at the dark condition . For example, the same experiment performed on the WO 3 nanoflake array photoanode reveals that its photocurrent density drops significantly from the initial 0.3 mA/cm 2 to <0.1 mA/cm 2 in 500 s (Figure d).…”

mentioning

confidence: 85%

CuWO₄ Nanoflake Array-Based Single-Junction and Heterojunction Photoanodes for Photoelectrochemical Water Oxidation

Chen

Zhao

et al. 2016

ACS Appl. Mater. Interfaces

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Over recent years, tremendous efforts have been invested in the search and development of active and durable semiconductor materials for photoelectrochemical (PEC) water splitting, particularly for photoanodes operating under a highly oxidizing environment. CuWO4 is an emerging candidate with suitable band gap and high chemical stability. Nevertheless, its overall solar-to-electricity remains low because of the inefficient charge separation process. In this work, we demonstrate that this problem can be partly alleviated through designing three-dimensional hierarchical nanostructures. CuWO4 nanoflake arrays on conducting glass are prepared from the chemical conversion of WO3 templates. Resulting electrode materials possess large surface areas, abundant porosity and small thickness. Under illumination, our CuWO4 nanoflake array photoanodes exhibit an anodic current density of ∼0.4 mA/cm(2) at the thermodynamic potential of water splitting in pH 9.5 potassium borate buffer--the largest value among all available CuWO4-based photoanodes. In addition, we demonstrate that their performance can be further boosted to >2 mA/cm(2) by coupling with a solution-cast BiVO4 film in a heterojunction configuration. Our study unveils the great potential of nanostructured CuWO4 as the photoanode material for PEC water oxidation.

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confidence: 85%

CuWO₄ Nanoflake Array-Based Single-Junction and Heterojunction Photoanodes for Photoelectrochemical Water Oxidation

Chen

Zhao

et al. 2016

ACS Appl. Mater. Interfaces

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“…Similar conclusions can be made; W is clearly a base metal, with a stable domain in the physiological pH range (x-y) (5.6 to 9.0 [14]) only outside of the water window (a-b). Heumann and Stolica and others still do refer to tungsten's "protective film" of WO2 [18] what may be termed a protective or passive oxide film may continually form at all pH values, inhibiting dissolution to some degree [46]. However, the long term behaviour remains continual dissolution into soluble hexavalent W 6+ .…”

Section: Corrosion Thermodynamics and Pourbaix Diagramsmentioning

confidence: 99%

“…W has often been referred to as having 'excellent corrosion resistance' [3], and in some biomaterials literature as 'inert' and 'stable' [16,17] in aqueous solutions [18]. However, in the presence of water, at 25 °C under 1 atm pressure, metallic W is not thermodynamically stable [14,19,20].…”

Section: Corrosionmentioning

confidence: 99%

“…In solutions of neutral and alkaline pH values, the W x O y surface species form soluble tungstate ions (often represented as 'orthotungstate' 4 [32]), which results in the continual dissolution of surface material; these are the products of W oxide dissolution as well as active W metal dissolution at higher pHs [23,[33][34][35]. All authors agree that in neutral to alkaline aqueous environments, the oxide phase on the metal surface hydrates, and then passes into solution as these hexavalent tungstate ions [18,33,34,[36][37][38][39][40][41][42]]. Weidman's chronoamperometry measurements at 1.0 V sweeping from pH 0.5 to 13.0 presented sharp increases in current densities between pH 4-6, indicating that there is no passivation occurring via oxidation at higher pH values [22].…”

Section: Corrosion Thermodynamics and Pourbaix Diagramsmentioning

confidence: 99%

“…Heumann et al [18] still refer to tungsten's 'protective film' of WO 2 -what may be termed a protective or passive oxide film may continually form at all pH values, inhibiting dissolution to some degree [46]. However, the long-term behaviour remains as continual dissolution into soluble hexavalent W 6+ .…”

Section: Corrosion Thermodynamics and Pourbaix Diagramsmentioning

confidence: 99%

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The use of tungsten as a chronically implanted material

Idil

Donaldson

2018

J. Neural Eng.

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This review paper shows that tungsten should not generally be used as a chronically implanted material. The metal has a long implant history, from neuroscience, vascular medicine, radiography, orthopaedics, prosthodontics, and various other fields, primarily as a result of its high density, radiopacity, tensile strength, and yield point. However, a crucial material criterion for chronically implanted metals is their long-term resistance to corrosion in body fluids, either by inherently noble metallic surfaces, or by protective passivation layers of metal oxide. The latter is often assumed for elemental tungsten, with references to its 'inertness' and 'stability' common in the literature. This review argues that in the body, metallic tungsten fails this criterion, and will eventually dissolve into the soluble hexavalent form W, typically represented by the orthotungstate [Formula: see text] (monomeric tungstate) anion. This paper outlines the metal's unfavourable corrosion thermodynamics in the human physiological environment, the chemical pathways to either metallic or metal oxide dissolution, the rate-limiting steps, and the corrosion-accelerating effects of reactive oxidising species that the immune system produces post-implantation. Multiple examples of implant corrosion have been reported, with failure by dissolution to varying extents up to total loss, with associated emission of tungstate ions and elevated blood serum levels measured. The possible toxicity of these corrosion products has also been explored. As the field of medical implants grows and designers explore novel solutions to medical implant problems, the authors recommend the use of alternative materials.

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Critical Pitting Potentials of Tungsten in lithium chloride‐methanol‐water solutions

Stolica

1976

Materials & Corrosion

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The critical pitting potentials of tungsten were determined in 0.5 M LiCl ‐ X M H2O ‐ methanol solutions where X ranged from 0 to 55. They were obtained from potentiostatic current time curves measured by two different methods: (1) The potential of the electrode in solution was brought to the desired value at a definite rate of potential change (2) Dry electrodes were immersed into the solution under applied potential. At water concentrations up to 11. M the cpp's obtained by (1) and (2) are less than 2 V vs Ag/AgCl/0.5 M LiCl(aq). The cpp's obtained by method (1) are 52 V, 62 V (maximum value) and 33 V for solutions having 14. M, 28. M and 55. M H2O, respectively. The cpp's obtained by method (2) are about as half as large as those of (1) with the exception of the values for 14. M and 17. M H2O, which are about 4/5 as large. The shape of the cpp‐water concentration curve is similar to that of the viscosity‐concentration curve of 1 M LiCl–H2O‐methanol solutions given in the literature. A mechanism for chloride ion attack of the film involving the formation of WO2Cl2 is proposed.

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The electrochemical behaviour of tungsten—I. The dissolution of tungsten and tungsten oxides in buffer solutions

Cited by 27 publications

References 3 publications

CuWO₄ Nanoflake Array-Based Single-Junction and Heterojunction Photoanodes for Photoelectrochemical Water Oxidation

CuWO₄ Nanoflake Array-Based Single-Junction and Heterojunction Photoanodes for Photoelectrochemical Water Oxidation

The use of tungsten as a chronically implanted material

Critical Pitting Potentials of Tungsten in lithium chloride‐methanol‐water solutions

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The electrochemical behaviour of tungsten—I. The dissolution of tungsten and tungsten oxides in buffer solutions

Cited by 27 publications

References 3 publications

CuWO4 Nanoflake Array-Based Single-Junction and Heterojunction Photoanodes for Photoelectrochemical Water Oxidation

CuWO4 Nanoflake Array-Based Single-Junction and Heterojunction Photoanodes for Photoelectrochemical Water Oxidation

The use of tungsten as a chronically implanted material

Critical Pitting Potentials of Tungsten in lithium chloride‐methanol‐water solutions

Contact Info

Product

Resources

About

CuWO₄ Nanoflake Array-Based Single-Junction and Heterojunction Photoanodes for Photoelectrochemical Water Oxidation

CuWO₄ Nanoflake Array-Based Single-Junction and Heterojunction Photoanodes for Photoelectrochemical Water Oxidation