PEM electrolysis uses ion-conducting solid polymers instead of electrolytes to produce electrolytic reactions. When a voltage is applied between the two electrodes, the negatively charged oxygen in the water molecule will provide its electrons, thereby generating protons, electrons and O2 at the anode. H + ions flow to the cathode through the proton-conducting polymer, where they absorb electrons and become neutral H atoms. These combinations form H 2 at the cathode. The electrolyte and the two electrodes are sandwiched between two bipolar plates, which transport water into them, transport product gas out of the battery, conduct electricity and circulate coolant to cool the process. PEM water electrolysis is a promising energy storage technology with fast dynamic response time, wide adjustable working range and high gas production efficiency, and can be perfectly combined with renewable energy.