Monitoring and control of water quality for water electrolyzer used to generate hydrogen

A method of monitoring and controlling water quality for a water electrolyzer, the method comprising:

• operating a water electrolysis cell having a solid polymer electrolyte membrane that generates hydrogen and oxygen through electrolysis of a feed water supplied to the water electrolysis cell in a closed loop with excess water discharged from the water electrolysis cell recycled back as the feed water;
• measuring, with a fluoride ion sensor, a fluoride ion concentration in the excess water to provide a measured fluoride ion concentration in the excess water;
• comparing, by one or more processors, the measured fluoride ion concentration to a fluoride ion concentration threshold;
• and
• when the measured fluoride ion concentration is above the fluoride ion concentration threshold, terminating closed loop operation of the water electrolysis cell by at least supplying ultrapure water from an ultrapure water generation system to the water electrolysis cell.

A water electrolysis system comprising:

• a water electrolysis cell having a solid polymer electrolyte membrane, wherein the water electrolysis cell is configured to receive a feed water and generate hydrogen and oxygen through electrolysis of the feed water, and the water electrolysis cell is further configured to discharge excess water from the water electrolysis cell;
• a fluoride ion sensor positioned to measure a fluoride ion concentration in the excess water to provide a measured fluoride ion concentration in the excess water;
• an ultrapure water generation system in selective fluid communication with the water electrolysis cell;
• and
• a controller configured to:
• receive the measured fluoride ion concentration from the fluoride ion sensor;
• compare the measured fluoride ion concentration to a fluoride ion concentration threshold;
• if the measured fluoride ion concentration is below the fluoride ion concentration threshold, control recycling of the excess water as the feed water to the water electrolysis cell;
• and
• if the measured fluoride ion concentration is above the fluoride ion concentration threshold, control supply of ultrapure water to the water electrolysis cell from the ultrapure water generation system.