Depolarized cathodes

Guild AF, Gancs L, Allen RJ, Mukerjee S (2007) Carbon-supported low-loading rhodium sulfide electrocatalysts for oxygen depolarized cathode applications. Appl Catal A 326 227-235... 

Meyers, J. P. Villwock, R. D. Darling, R. M. Newman, J. In Advances In Mathematical Modeling and Simulation of Electrochemical Processes and Oxygen Depolarized Cathodes and Activated Cathodes for Chlor-Alkall Processes, Van Zee, J. W., Puller, T. P., Poller, P. C., Hine, P., Eds. The Electrcohemical Society Proceedings Series Pennington, NJ, 1998 Vol. PV 98-10. 

Dioxygen is also evolved at the anode. An alternative cathodic reaction is the reduction of dioxygen using oxygen depolarized cathodes. Here, the anodic reaction is the same as above, while the cathodic reaction is ... 

Fig. 14 Schematic representation of the chlor-alkali electrolysis using an oxygen depolarized cathode.

Oxygen depolarized cathodes can be used in hydrochloric acid electrolysis, too. 

Fig. 17 Scheme of producing chlorine from hydrochloric acid using an Oxygen Depolarized Cathode (ODC). The ODC/catalyst/membrane unit is displayed in more detail in the coming Figure 23. 

As is the case with fuel cells, depolarized cathodes have been considered for years but have not yet found wide commercial use in the chlor-alkali indusby. Reports of work in the 1970s and 1980s [117,118] described the use of solid-polymer electrolyte systems. Microporous electrodes are necessary for electrical continuity in these cells, and the cathode reaction takes place in the interior of the gas-diffiision electrode. Operating deficiencies include the gradual penetration of gas channels by caustic solution and the possibility of bulk flow of catholyte into the gas side of the electrodes. Section 17.2.2.2 describes more recent work that addresses these deficiencies. The first conunercial applications are beginning to appear. 

Recent developments in cell technology include the use of ion-exchange membranes instead of diaphragms [29] and the use of oxygen-depolarized cathodes [30]. Section 11.2.2.2C discusses the latter as an alternative to the standard cathode that reduces the reversible potential by about 1.23 V. Section 17.2.2.2 identifies these cathodes as an important emerging technology. A commercial plant for production of about 24,000 tons of chlorine by electrolysis of HCl with depolarized cathodes was recently announced [31]. 

Mine and coworkers [53,54] used a depolarized cathode with an HCl cell to recover chlorine from dilute waste gas. The gas, fed to the cathode compartment, oxidizes cuprous chloride in the bulk of the solution ... 

Commercial operation of a plant for the electrolysis of HCl using depolarized cathodes is now underway [26]. There are plans to expand the capacity to 20,000 tons per year of chlorine. 

A. Uchimura, H. Aikawa, K. Saiki, A. Sakata, and N. Furuya, Gas Diffusion Electrode Using Porous Nickel. In J.W. Van Zee, P.C. Eoller, T.F. Fuller, and F. Hine (eds.). Advances in Mathematical Modelling and Simulation ofElectrochemical Processes and Oxygen Depolarized Cathodes and Activated Cathodes for Chlor-Alkali and Chlorate Processes, Proc. vol. 98-10, The Electrochemical Society, Pennington, NJ (1998), p. 220. 

F. Gestermann and A. Ottaviani, Chlorine Production with Oxygen-Depolarized Cathodes on an Industrial Scale. In J. Moorhouse (ed.). Modem Chlor-Alkali Technology, vol. 8, Blackwell Science, Oxford (2001), p.49. 

L. Lipp, S. Gottesfeld and J. Chlistunoff, Peroxide formation in a zero-gap chlor-alkali cell with an oxygen-depolarized cathode . Journal of Applied Electrochemistry, 35 (2005) 1015. 

Main directions to lower the cell voltage are a cathode that is stable, active, and selective for hydrogen evolution, alternatively an oxygen-depolarized cathode. Operation at higher temperature, 90-100 °C, would lower the cell voltage but is today limited by the materials used in the process. 

Chlorine and Caustic Technology, Using Oxygen Depolarized Cathode... 

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