Disclosure of the internal mechanism during activating a proton exchange membrane fuel cell based on the three-step activation method

In our previous peer-reviewed article, a three-step method is put forward for increasing the efficiency of activating a newly-built membrane electrode assembly (MEA). By changing the activation temperatures of each step of the three-step method, the fuel cell performance can be greatly improved when compared with a normal one-step activation method. In this article, a deep understanding of the internal mechanism of this three-step method is conducted. Both cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) are tested after each I–V test round of a step. Two indexes, i.e., resistance reducing rate and effective current generation of catalyst (ECGC), are put forward. By integrating these two indexes, it clearly shows that the three-step activation method includes two effects, i.e., pore digging effect and pore swelling effect, which dominates in Step 1 and Step 2 separately. Finally, a pore forming mechanism model is put forward, which explains that the pore digging effect helps to form more three-phase reaction points and the pore swelling effect helps the three-phase points to become more effective. The same model also explains why the electrochemical surface area (ECSA) decreases during Step 1 and Step 2.