Electrode material, electrode, and method for hydrogen chloride electrolysis

Abstract

An electrode material, an electrode and a process for hydrogen chloride electrolysis based on platinum metal as catalyst, in which the electrode material has a nanosize mixture of platinum particles and silver particles, is described.

1 .- 21 . (canceled) 
     
     
         22 . An electrode material for hydrogen chloride electrolysis which is based on platinum metal as catalyst, wherein the electrode material has a nanosize mixture of platinum particles and silver particles, wherein the platinum and silver particles have a particle diameter of essentially not more than 1 μm. 
     
     
         23 . The electrode material as claimed in  claim 22 , wherein the weight ratio of platinum to silver is from 10:90 to 90:10. 
     
     
         24 . The electrode material as claimed in  claim 22 , wherein the electrode material additionally comprises particles comprising alloys of platinum and silver. 
     
     
         25 . The electrode material as claimed  claim 22 , wherein the platinum particles, silver particles, and alloy particles have, independently of one another, an average particle diameter in the range of from 1 nm to 100 nm. 
     
     
         26 . The electrode material as claimed in  claim 22 , wherein the platinum and silver particles form agglomerates having an average agglomerate diameter of less than 100 μm. 
     
     
         27 . The electrode material as claimed in  claim 22 , wherein the platinum and silver particles are obtained by simultaneous electrodeposition of platinum and silver from platinum and silver salt solutions or melts onto an electrically conductive support material. 
     
     
         28 . The electrode material as claimed in  claim 27 , wherein the electrodeposition is carried out using a pulsed voltage and is carried out at an open-circuit voltage of from 0.4 to 0.8 V measured relative to a silver-silver chloride reference electrode in 3 molar potassium chloride solution, using voltage pulses in the range from −0.4 to −0.8 V and a pulse length in the range from 5 to 100 ms. 
     
     
         29 . A chlorine-resistant electrode for electrochemical processes which comprises an electrode material based on a mixture of platinum and silver, wherein the electrode can be installed as a cathode in hydrogen chloride electrolysis. 
     
     
         30 . A chlorine-resistant electrode for electrochemical processes which comprises the electrode material as claimed in  claim 22 . 
     
     
         31 . The electrode as claimed in  claim 29 , wherein the electrode is an oxygen-consuming cathode. 
     
     
         32 . The electrode as claimed in  claim 31 , wherein the electrode is configured as a gas diffusion electrode having an electrically conductive sheet-like textile structure as support, wherein at least one side of the electrode comprises a catalyst which comprises the electrode material and optionally additionally comprises at least one binder comprising fluorine compounds incorporated therein. 
     
     
         33 . The electrode as claimed in  claim 32 , wherein the conductive sheet-like structure is provided on one or both sides with a coating which comprises at least one fluoropolymer and at least one electrically conductive carbon material and is additionally coated on only one side with a mixture of the catalyst and at least one fluoropolymer. 
     
     
         34 . The electrode as claimed in  claim 29 , wherein the electrode is a hydrogen-evolving cathode. 
     
     
         35 . The electrode as claimed in  claim 34 , wherein the electrode is a graphite electrode in which the electrode material is applied as a catalytically active coating to a graphite support. 
     
     
         36 . A membrane-electrode assembly which comprises an ion-exchange membrane which is provided on at least one side with a catalyst comprising the electrode material as claimed in  claim 22 . 
     
     
         37 . An electrochemical cell comprising at least an anode chamber comprising an anode and a cathode chamber comprising a cathode, wherein the anode and the cathode are separated from one another by a separator, and wherein the cathode is the electrode as claimed in  claim 29 . 
     
     
         38 . The electrochemical cell as claimed in  claim 37 , wherein the separator is an ion-exchange membrane or a diaphragm. 
     
     
         39 . An electrochemical cell comprising at least an anode chamber comprising an anode and a cathode chamber comprising a cathode, wherein the anode and the cathode are separated from one another by a separator, and wherein the separator is configured as the membrane-electrode assembly as claimed in  claim 36 . 
     
     
         40 . The electrochemical cell as claimed in  claim 37 , wherein the anode chamber can be supplied with aqueous hydrochloric acid and the cathode chamber can be supplied with an oxygen-containing gas or with an aqueous hydrochloric acid. 
     
     
         41 . A process for the electrolysis of an aqueous hydrochloric acid solution to form chlorine, wherein aqueous hydrochloric acid is fed into the anode chamber and an oxygen-containing gas is fed into the cathode chamber in an electrochemical cell as claimed in  claim 37  while the electrochemical cell is supplied with an electric direct current.