Electrochemistry

Wendt, Hartmut; Vogt, Helmut; Kreysa, G.; Kolb, Dieter M.; Engelmann, Gerald E.; Ziegler, Jörg C.; Goldacker, H.; Jüttner, K.; Galla, U.; Schmieder, H.; Steckhan, Eberhard

doi:10.1002/14356007.a09_183.pub3

Cited by 3 publications

(5 citation statements)

References 203 publications

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“…In aprotic solvents this is obviously not the case. However, for the formation of fuels, protons are needed and in aprotic solvents CO and oxalates are the main products [45]. Moreover, currently reported densities are low.…”

Section: Reaction Pathwaysmentioning

confidence: 99%

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Functioning devices for solar to fuel conversion

Mul¹,

Schacht²,

Swaaij³

et al. 2012

Chemical Engineering and Processing: Process Intensification

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a b s t r a c tThis paper provides a perspective on the technologies capable of converting solar energy, CO 2 and H 2 O into an easy to use fuel. The paper addresses bio-based approaches, but mainly focuses on (i) the combination of photovoltaic (PV) devices and electrocatalysis, (ii) single unit operation by photocatalytic conversion, and (iii) solar thermal conversion. Each option is described in a general manner, including a brief evaluation of the advantages and disadvantages. Also suggestions for future research endeavours are given. Based on the used literature data, for electrocatalytic and photocatalytic technologies, dramatic improvements should be made in material optimization, as well as reactor design and operation. Large efficiency gains are necessary to enable use of these technologies in practice. Solar thermal conversion is more mature, and requires specific optimization in processing, as will be discussed.

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Section: Reaction Pathwaysmentioning

confidence: 99%

“…This implies that the electrolysis cell should work at high pressure. In practice, a commercial process already exists [45]. Compared to the previous processes, reduction of CO 2 by H 2 by classical methanol synthesis catalysis is rather straightforward, see scheme in Fig.…”

Section: Processes 2251 Conversion Of Co 2 Into Fuels By Electrocmentioning

confidence: 99%

Functioning devices for solar to fuel conversion

Mul¹,

Schacht²,

Swaaij³

et al. 2012

Chemical Engineering and Processing: Process Intensification

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show abstract

“…The usage of mercury cells in the European Union is scheduled to be discontinued in 2017 . Typical conditions applied in the membrane process are shown in Table , and more detailed descriptions of the three technologies can be found in, for example, Wendt et al or Schmittinger et al A small percentage of the total chlorine production is based on electrolysis of 17 wt % HCl in either diaphragm or membrane cells . The energy cost for the production is usually given in terms of kWh t –1 NaOH produced, with 886 kg Cl 2 being produced per tonne of NaOH.…”

Section: Introductionmentioning

confidence: 99%

“…The pH that is used in the chlorate process is chosen to prevent chlorine gas formation, which increases in rate at lower pH, and oxygen gas formation, which increases in rate at higher pH. Chlorate cells usually have a large volume tank through which the reaction solution flows to allow reaction to reach high conversion. ,, The process temperature is kept high to increase the rate of reaction (enabling the usage of a smaller reaction vessel) and of the electrode reactions (lowering the cell voltage). ,− However, the rate of parasitic oxygen evolution also increases with increasing temperature, meaning that the temperature chosen is a balance between minimizing the rate of oxygen evolution and maximizing the reaction rates of the desired reactions…”

Section: Introductionmentioning

confidence: 99%

Selectivity between Oxygen and Chlorine Evolution in the Chlor-Alkali and Chlorate Processes

2016

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Chlorine gas and sodium chlorate are two base chemicals produced through electrolysis of sodium chloride brine which find uses in many areas of industrial chemistry. Although the industrial production of these chemicals started over 100 years ago, there are still factors that limit the energy efficiencies of the processes. This review focuses on the unwanted production of oxygen gas, which decreases the charge yield by up to 5%. Understanding the factors that control the rate of oxygen production requires understanding of both chemical reactions occurring in the electrolyte, as well as surface reactions occurring on the anodes. The dominant anode material used in chlorate and chlor-alkali production is the dimensionally stable anode (DSA), Ti coated by a mixed oxide of RuO2 and TiO2. Although the selectivity for chlorine evolution on DSA is high, the fundamental reasons for this high selectivity are just now becoming elucidated. This review summarizes the research, since the early 1900s until today, concerning the selectivity between chlorine and oxygen evolution in chlorate and chlor-alkali production. It covers experimental as well as theoretical studies and highlights the relationships between process conditions, electrolyte composition, the material properties of the anode, and the selectivity for oxygen formation.

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“…The high electrocatalytic activity of RuO 2 in the hydrogen evolution reaction (HER) has been known for more than 40 years . However, the main industrial use of RuO 2 -based electrodes is in anodic reactions, such as the production of chlorine gas or sodium chlorate. , Nevertheless, RuO 2 -coated Ti or Ni electrodes for HER have been investigated and are applied in industry, , prompting interest in the stability of such coatings during HER. , It has been found that structural changes, namely, an expansion of the rutile lattice, occur during hydrogen evolution using both RuO 2 and IrO 2 coatings. − These changes are associated with an activation of the electrode. ,, However, they have also been connected with the degradation of the electrode upon exposure to reverse currents that might occur when an industrial chlor-alkali or chlorate electrolyzer is shut down . Näslund et al have presented an in-depth XPS and X-ray diffraction (XRD) study of RuO 2 electrodes that had been used for HER, where XPS and XRD spectra were measured with several time delays after hydrogen evolution at a RuO 2 coating deposited on Ni.…”

Section: Introductionmentioning

confidence: 99%

Structural Changes in RuO₂ during Electrochemical Hydrogen Evolution

2016

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A comprehensive theoretical study of the X-ray photoelectron shifts for RuO 2 during hydrogen evolution has been performed. The shifts have been calculated using firstprinciples density functional theory and are compared with previous theoretical and experimental results to reconsider the proposed structural changes occurring during hydrogen evolution on RuO 2 . We find that during hydrogen evolution hydrogen enters the rutile RuO 2 lattice and converts oxygen groups into hydroxyl groups and that this process explains the experimentally observed increase in unit cell dimensions as well as observed chemical shifts. Furthermore, carbon contamination is the most likely explanation for a set of peaks previously identified as caused by a new RuO(OH) 2 phase. We find that formation of metallic Ru is just one possible explanation for another peak in the X-ray photoelectron spectrum and that explanations including conversion of RuO 2 into Ru(OH) 3 , or removal of oxygen from Ru active surface sites, also can explain the observed shifts.

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Electrochemistry

Cited by 3 publications

References 203 publications

Functioning devices for solar to fuel conversion

Functioning devices for solar to fuel conversion

Selectivity between Oxygen and Chlorine Evolution in the Chlor-Alkali and Chlorate Processes

Structural Changes in RuO₂ during Electrochemical Hydrogen Evolution

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Electrochemistry

Cited by 3 publications

References 203 publications

Functioning devices for solar to fuel conversion

Functioning devices for solar to fuel conversion

Selectivity between Oxygen and Chlorine Evolution in the Chlor-Alkali and Chlorate Processes

Structural Changes in RuO2 during Electrochemical Hydrogen Evolution

Contact Info

Product

Resources

About

Structural Changes in RuO₂ during Electrochemical Hydrogen Evolution