New Developments in Electrode Coatings for Chlor-Alkali Processes

Couper, A. M.; Brooks, W. N.; Denton, D. A.

doi:10.1007/978-94-009-1137-6_8

Cited by 1 publication

(5 citation statements)

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“…Unfortunately, many studies lack important details regarding the properties of the anode. For example, proprietary coatings of unnamed composition that lead to lower oxygen evolution rates have been used in several experimental studies. ,,, Most studies have focused only on the selectivity between oxygen and chlorine formation under chlor-alkali conditions. An exception is the study of a modified coating with decreased selectivity for oxygen evolution at chlorate conditions performed by Spasojević et al − Additionally, detailed characterization, such as of the actual composition of the final coating has usually not been reported in literature, even if studies on proprietary anodes are excluded.…”

Section: Discussionmentioning

confidence: 99%

“…The effect of altering the relative amounts of Ru and Ti in RTO coatings will be discussed first. A decrease in the Ru content has consistently been shown to result in decreased selectivity for oxygen evolution (refs , , , , , , , and ). Similar trends regarding Ru content and OER selectivity have been noted for Ru–Sn oxide electrodes .…”

Section: Discussionmentioning

confidence: 99%

“…Similar trends regarding Ru content and OER selectivity have been noted for Ru–Sn oxide electrodes . This might be another aspect on the observation that an increased overpotential for oxygen evolution of an anode material (i.e., a decreased j 0 for reaction ) has been linked to a decreased selectivity for oxygen evolution in chloride-containing solutions. ,,, These factors have been related to mechanistic differences between the oxygen-evolving reaction and the chlorine-evolving reaction. It has been proposed that both reactions need Ru sites to progress, but that the oxygen-evolving reaction needs two Ru adjacent sites. , Here an interesting new insight can be gained from the DFT studies by Rossmeisl et al, Hansen et al, and of Exner et al , In these studies, the importance of adjacent CUSs on the anode surface were considered.…”

Section: Discussionmentioning

confidence: 99%

“…It took studies where the proper detection of the oxygen evolved was performed to find that other reactions might also be important sources of oxygen. Nevertheless, some still do not agree that anodic decomposition of hypochlorite species is important, , warranting further studies of how hypochlorite is actually decomposed at the anode. The relative importance of heterogeneous chemical decomposition and electrocatalytic decomposition of hypochlorite species on, for example, the RTO electrode surface, is also an open question.…”

Section: Discussionmentioning

confidence: 99%

“…Also in 1990, Couper et al reported further data for an ICI membrane chlor-alkali process anode coating. The coating, with unnamed composition, was an improvement of the previous low oxygen coatings , and had been developed for a high oxygen evolution overpotential.…”

Section: Selectivity For Oxygen and Chlorine Evolution In Chlor-alkal...mentioning

confidence: 99%

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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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