Electrochemical apparatus with retractable electrode

Abstract

Electrochemical apparatus and methods that support periodic, non-steady state, or discontinuous operation without suffering degradation of materials or loss of efficiency. The invention provides a means for positioning one or more electrodes into contact with electrolyte and means for retracting the one or more electrodes out of contact with the electrolyte. The means for positioning and means for retracting may be the same device or different devices. The means for positioning and means for retracting may be designed to provide automatic, passive, or fail-safe retraction of the electrode upon a given shutdown condition, such as a voltage of less than one Volt being applied between the first and second electrodes, expiration of a time period, an ozone concentration greater than a setpoint ozone concentration, contact pressure of less than 5 psig, and combinations thereof.

1 . An electrode, comprising:
 a porous metal substrate having a substantially nonporous metal current collector is at least partially embedded within the substrate; and   an electrical connector coupled to the metal current collector and extending from the porous metal substrate.   
     
     
         2 . The electrode of  claim 1 , wherein the porous metal substrate is sintered around metal current collector. 
     
     
         3 . The electrode of  claim 2 , wherein the metal current collector is entirely embedded within the porous metal substrate. 
     
     
         4 . The electrode of  claim 1 , wherein the electrical connector forms part of a shaft coupled to the porous metal substrate. 
     
     
         5 . The electrode of  claim 4 , characterized in that the porous metal substrate may be moved by actuating the shaft. 
     
     
         6 . A method for controlling the voltage applied to an ozone generator including an anode substrate with a lead dioxide anodic electrocatalyst, a cathode, and a proton exchange membrane in contact between the lead dioxide and the cathode, the method comprising:
 separating the lead dioxide out of contact with the proton exchange membrane if the voltage between the anode substrate and the cathode becomes less than a setpoint voltage.   
     
     
         7 . The method of  claim 6 , wherein the setpoint voltage is about one Volt. 
     
     
         8 . A method for generating ozone in an electrochemical cell having a cathode electrode, an anode electrode, an acidic electrolyte disposed between the anode electrode and the cathode electrode, and a voltage source coupled between the anode electrode and cathode electrode, the method comprising the steps of applying a voltage between the anode electrode and the cathode electrode characterised in that the method further comprises the steps of initially moving the anode electrode from a retracted position in which it is spaced from the electrolyte to an operative position in which it is in contact with the electrolyte, and turning the voltage source on before or simultaneously with the engagement of the anode with the electrolyte, the method further comprising a step of retracting the anode electrode out of contact with the acidic electrolyte shortly before or simultaneously with turning off the voltage source. 
     
     
         9 . The method of  claim 8  wherein the acidic electrolyte is a proton exchange membrane and wherein the one or more standby conditions includes a contact pressure of less than 10 psig of the anode electrode with the proton exchange membrane. 
     
     
         10 . The method of  claim 8  wherein the engagement of the anode electrode into contact with the electrolyte is effected in response to the sensing of one or more production conditions. 
     
     
         11 . The method of  claim 10  wherein the one or more production conditions are selected from:
 a voltage greater than one volt being applied between the first and second electrodes, the expiration of a time period from termination of operation of the cell, and an ozone concentration less than a set point ozone concentration within the cell.