Flexible Seven-in-One Microsensor Embedded in High-Pressure Proton Exchange Membrane Water Electrolyzer for Real-Time Microscopic Monitoring.

The voltage, current, temperature, humidity, pressure, flow, and hydrogen in the high-pressure proton exchange membrane water electrolyzer (PEMWE) can influence its performance and life. For example, if the temperature is too low to reach the working temperature of the membrane electrode assembly (MEA), the performance of the high-pressure PEMWE cannot be enhanced. However, if the temperature is too high, the MEA may be damaged. In this study, the micro-electro-mechanical systems (MEMS) technology was used to innovate and develop a high-pressure-resistant flexible seven-in-one (voltage, current, temperature, humidity, pressure, flow, and hydrogen) microsensor. It was embedded in the upstream, midstream, and downstream of the anode and cathode of the high-pressure PEMWE and the MEA for the real-time microscopic monitoring of internal data. The aging or damage of the high-pressure PEMWE was observed through the changes in the voltage, current, humidity, and flow data. The over-etching phenomenon was likely to occur when this research team used wet etching to make microsensors. The back-end circuit integration was unlikely to be normalized. Therefore, this study used lift-off process to further stabilize the quality of the microsensor. In addition, the PEMWE is more prone to aging and damage under high pressure, so its material selection is very important.

Long-Acting Real-Time Microscopic Monitoring Inside the Proton Exchange Membrane Water Electrolyzer.

The proton exchange membrane water electrolyzer (PEMWE) requires a high operating voltage for hydrogen production to accelerate the decomposition of hydrogen molecules so that the PEMWE ages or fails. According to the prior findings of this R&D team, temperature and voltage can influence the performance or aging of PEMWE. As the PEMWE ages inside, the nonuniform flow distribution results in large temperature differences, current density drops, and runner plate corrosion. The mechanical stress and thermal stress resulting from pressure distribution nonuniformity will induce the local aging or failure of PEMWE. The authors of this study used gold etchant for etching, and acetone was used for the lift-off part. The wet etching method has the risk of over-etching, and the cost of the etching solution is also higher than that of acetone. Therefore, the authors of this experiment adopted a lift-off process. Using the flexible seven-in-one (voltage, current, temperature, humidity, flow, pressure, oxygen) microsensor developed by our team, after optimized design, fabrication, and reliability testing, it was embedded in PEMWE for 200 h. The results of our accelerated aging test prove that these physical factors affect the aging of PEMWE.