System and methods of water electrolysis

Abstract

Provided herein are methods for cleaning a diaphragm and/or membrane in an electrolysis system. For example, provided herein is a method of chemically cleaning a diaphragm and/or membrane comprising immersing the diaphragm and/or membrane in an acidic medium, immersing the diaphragm and/or membrane in a weak alkaline medium, and rinsing the diaphragm and/or membrane with deionized water. Also provided herein is a method of electrochemically cleaning a diaphragm and/or membrane comprising reversing the direction of current applied across the diaphragm and/or membrane, applying a cathodic current to the electrolyte solution, applying an anodic current to the electrolyte solution, rinsing the diaphragm and/or membrane with deionized water, and removing deposits from the electrolyte solution. Also provided herein is a method of mechanically cleaning a diaphragm and/or membrane comprising applying a voltage across the diaphragm and/or membrane that is higher than the normal operating voltage, and mechanically agitating the electrolyte solution.

What is claimed is: 
     
         1 . A method of chemically cleaning a diaphragm and/or membrane in an alkaline electrolysis system, the method comprising:
 immersing the diaphragm and/or membrane in an acidic medium;   immersing the diaphragm and/or membrane in a weak alkaline medium; and   rinsing the diaphragm and/or membrane with deionized water.   
     
     
         2 . The method of  claim 1 , wherein the acidic medium comprises at least one acid selected from the group consisting of sulfuric acid, citric acid, acetic acid, and mixtures thereof. 
     
     
         3 . The method of  claim 2 , wherein the acidic medium comprises the at least one acid in a concentration of from about 0.01% by weight to about 5% by weight. 
     
     
         4 . The method of  claim 1 , wherein immersing the diaphragm and/or membrane in an acidic medium further comprises first immersing the diaphragm and/or membrane in a first acidic medium comprising a first acid, and subsequently immersing the diaphragm and/or membrane in a second acidic medium comprising a second acid. 
     
     
         5 . The method of  claim 4 , wherein the first acidic medium comprises sulfuric acid in a concentration of from about 0.5% by weight to about 2% by weight. 
     
     
         6 . The method of  claim 4 , wherein the first acidic medium comprises citric acid in a concentration of from about 0.1% by weight to about 0.5% by weight. 
     
     
         7 . The method of  claim 1 , wherein the weak alkaline medium comprises at least one base selected from the group consisting of sodium bicarbonate, potassium bicarbonate, sodium borate, potassium borate, and mixtures thereof. 
     
     
         8 . The method of  claim 7 , wherein the weak alkaline medium comprises sodium bicarbonate in a concentration of from about 0.1% by weight to about 0.5% by weight. 
     
     
         9 . The method of  claim 1 , wherein rinsing the diaphragm and/or membrane further comprises immersing the diaphragm and/or membrane in deionized water for a period of at least about 5 minutes. 
     
     
         10 . A method of electrochemically cleaning a diaphragm and/or membrane in an alkaline electrolysis system comprising an electrolyte solution, the method comprising:
 reversing a direction of current applied across the diaphragm and/or membrane;   applying a cathodic current to the electrolyte solution;   applying an anodic current to the electrolyte solution;   rinsing the diaphragm and/or membrane with deionized water; and   removing deposits from the electrolyte solution.   
     
     
         11 . The method of  claim 10 , wherein reversing a direction of current applied across the diaphragm and/or membrane further comprises applying a voltage across the diaphragm and/or membrane, wherein said voltage is less than about 0.6V RHE . 
     
     
         12 . The method of  claim 10 , wherein the applied cathodic current is constant. 
     
     
         13 . The method of  claim 10 , wherein the applied cathodic current is pulsed. 
     
     
         14 . The method of  claim 10 , wherein the applied anodic current is constant. 
     
     
         15 . The method of  claim 10 , wherein the applied anodic current is pulsed. 
     
     
         16 . The method of  claim 10 , wherein rinsing the diaphragm and/or membrane further comprises immersing the diaphragm and/or membrane in deionized water for a period of at least about 5 minutes. 
     
     
         17 . The method of  claim 10 , further comprising passing the electrolyte solution through a filter, an ion exchange resin, or a combination thereof. 
     
     
         18 . A method of mechanically cleaning a diaphragm and/or membrane in an alkaline electrolysis system, the method comprising:
 applying a voltage across the diaphragm and/or membrane that is higher than a normal operating voltage, thereby generating a stronger flow of gas bubbles within the electrolyte solution; and   mechanically agitating the electrolyte solution.   
     
     
         19 . The method of  claim 18 , wherein the voltage applied across the diaphragm and/or membrane is from about 1.05 to about 1.2 times greater than the normal operating voltage. 
     
     
         20 . The method of  claim 18 , wherein the electrolyte solution is agitated by sonication.