Water Electrolysis Shutdown via Voltage-Assisted Hydrogen Reabsorption
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Solution Overview
Problem
High-pressure hydrogen manufacturing apparatuses face challenges in safely reducing hydrogen pressure to prevent damage to solid polymer membranes and seals, leading to prolonged shutdown times and catalyst deterioration due to hydrogen leakage from cathode to anode during shutdown.
Innovation Solution
Applying a voltage between current collectors after hydrogen supply stops and reducing pressure in the cathode electrolysis chamber while maintaining the voltage, causing leaked hydrogen to be protonated and returned to the cathode, preventing its accumulation in the anode chamber and protecting catalyst layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pressure of hydrogen is reduced slowly to protect the solid polymer membrane and seals, then the damage to membrane and seals is prevented, but the shutdown time becomes excessively long
Solution Approach 1:
Before reducing the hydrogen pressure, a voltage is applied to the current collectors to activate the membrane electrode assembly in advance. This preliminary action ensures that the catalyst layers are functional and ready to immediately reabsorb any hydrogen that leaks into the anode chamber during the pressure reduction process, thus allowing faster pressure reduction without compromising membrane protection.
2Loss of time
If the water electrolyzing process is stopped and hydrogen pressure is reduced rapidly, then the shutdown time is shortened, but the solid polymer membrane and seals are unduly damaged
Solution Approach 1:
A voltage is applied to the current collectors before and during the pressure reduction process to activate the catalyst layers in advance. This ensures that when hydrogen leaks into the anode chamber during rapid pressure reduction, the catalyst layers can immediately reabsorb the hydrogen through electrochemical reactions, preventing membrane damage while enabling rapid shutdown.
3Reliability
If the pressure reduction period is prolonged to protect the membrane, then the membrane is protected from damage, but hydrogen leaks to the anode side causing catalyst reduction and deterioration
Solution Approach 1:
A voltage is applied to the current collectors before pressure reduction to activate the catalyst layers. This preliminary activation enables the catalyst layers to immediately reabsorb any hydrogen that leaks into the anode chamber during pressure reduction, preventing catalyst deterioration while maintaining membrane protection.
Solution Approach 2:
The hydrogen that leaks from the cathode to the anode chamber during pressure reduction is converted from a harmful factor into a beneficial one. The applied voltage causes the leaked hydrogen to be reabsorbed by the anode catalyst layers through electrochemical reactions, transforming the leakage problem into an opportunity for catalyst activation and hydrogen utilization.
4Object-generated harmful factors
If a voltage is applied between current collectors during pressure reduction, then leaked hydrogen is reabsorbed preventing catalyst deterioration, but additional energy consumption occurs
Solution Approach 1:
Instead of applying a high voltage throughout the entire pressure reduction process, a voltage is applied only during the critical period when hydrogen leakage is most likely to occur. This partial application of voltage reduces energy consumption while still effectively preventing catalyst deterioration during the most vulnerable phase of shutdown.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables efficient shutdown and startup of water electrolysis apparatuses, maintaining electrolyzing efficiency and preventing catalyst deterioration, even with repeated activation and shutdown cycles.
Implementation Method 1
The hydrogen ions move through the solid polymer electrolyte membranes to the cathodes, where the hydrogen ions combine with electrons to generate hydrogen
Implementation Method 2
a voltage is applied between current collectors after the cathode electrolysis chamber stops supplying the hydrogen, and reducing a pressure in at least the cathode electrolysis chamber while the voltage is being applied between the current collectors
Data Source
AI summary
A water electrolysis apparatus applies an electrolysis voltage between current collectors disposed on the respective sides of an electrolyte membrane thereby to electrolyze water to generate oxygen in an anode electrolysis chamber and hydrogen in a cathode electrolysis chamber under a pressure higher than a normal pressure. The water electrolysis apparatus is shut down by applying a voltage between the current collectors after the cathode electrolysis chamber stops supplying the hydrogen, reducing a pressure in at least the cathode electrolysis chamber while the voltage is being applied, and stopping applying the voltage when the pressure in the cathode electrolysis chamber is equal to a pressure in the anode electrolysis chamber.