• Membrane Journal
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• v.25 no.3
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• pp.203-215
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• 2015

Chlor-alkali (CA) membrane process is based on salined water electrolysis employing cation condutive polymer electrolytes, which has been used for the conventional production of both sodium hydroxide and chlorine gas. The CA membrane process has advantages such as relatively low environmental impacts and fairly reduced energy consumption, when compared with diaphragm and mercury process. In this review articles, basic concepts, fundamental characteristics, key technologies of CA membrane process are dealt with in detail. In addition, advanced technologies associated with CA membrane process are described. They include zerogap and oxygen depolarized cathode technologies to improve energy efficiency during the electrolysis. Carbon dioxide mineralization technology will also be introduced as an example of hybridization with different technologies. Finally, current market trend in CA membrane process will be presented.

• Membrane Journal
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• v.26 no.2
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• pp.152-158
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• 2016

The Chlor-alkali (CA) membrane cell is a major electrolysis system to produce valued chemicals such as chlorine gas and sodium hydroxide. The CA membrane process has been attracted in the industries, since it has relatively low energy consumption when compared with other CA processes. The key component in CA process is perfluorinated sulfonic acid ionomer membranes, which provide ion-selectivity and barrier properties to produced gases. Unfortunately, there is limited information to determine which factors should be satisfied for CA applications. In this study, the influences of PFSA membranes on CA performances are disclosed. They include ion transport behaviors, gas evolution capability, and chemical/electrochemical resistances under CA operation conditions.

• Journal of Electrochemical Science and Technology
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• v.14 no.2
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• pp.105-119
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• 2023

The electrochemical chlorine evolution reaction (CER) is an important electrochemical reaction and has been widely used in chlor-alkali electrolysis, on-site generation of ClO^-, and Cl₂-mediated electrosynthesis. Although precious metal-based mixed metal oxides (MMOs) have been used as CER catalysts for more than half a century, they intrinsically suffer from a selectivity problem between the CER and parasitic oxygen evolution reaction (OER). Hence, the design of selective CER electrocatalysts is critically important. In this review, we provide an overview of the fundamental issues related to the electrocatalysis of the CER and design strategies for selective CER electrocatalysts. We present experimental and theoretical methods for assessing the active sites of MMO catalysts and the origin of the scaling relationship between the CER and the OER. We discuss kinetic analysis methods to understand the kinetics and mechanisms of CER. Next, we summarize the design strategies for new CER electrocatalysts that can enhance the reactivity of MMO-based catalysts and overcome their scaling relationship, which include the doping of MMO catalysts with foreign metals and the development of non-precious metal-based catalysts and atomically dispersed metal catalysts.

• Korean Chemical Engineering Research
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• v.49 no.6
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• pp.810-815
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• 2011

Concentrated water discharged from seawater desalination process contains a high concentration of $Na^+$ ion. Electrolysis was applied to synthesize NaOH solution from the highly concentrated NaCl solution. The effect of various operating parameters of composited laboratory-scale chlor-alkali (CA) membrane cell was investigated. The operating parameters such as membrane types (CIMS and Nafion membranes), pretreatment of the membrane, flow rate (73 mL/min~200 mL/min), initial $Na^+$ ion concentration (1.5 M, 3M and 5 M) and current (1.5A and 2A) were evaluated. It was observed that synthesis efficiency of NaOH solution with CIMS membrane was higher than that with Nafion membrane, but the durability of CIMS membrane on $Cl_2$ gas was poor. The synthesis efficiency of NaOH solution increased with increasing initial $Na^+$ ion concentration and current, while the efficiency decreased with increasing flow rate using Nafion membrane.