Measurement and separation of cathodic mass transport resistance in high temperature proton exchange membrane fuel cell
Ziqian Wang, Linlin Yang, Suli Wang, Hai Sun, Gongquan Sun
Abstract
High oxygen transport resistance in the cathode is a main cause of the low performance of high temperature proton exchange membrane fuel cell (HT-PEMFC), and therefore to determine the contribution of different mass transport processes to the oxygen transport resistance is beneficial to the subsequent research work. In this paper, the molecular diffusion resistance (RM) in the cathode was successfully calculated by measuring the limiting currents with using different diluent gases. And the oxygen transport resistance in phosphoric acid (RPA) was analyzed by changing the humidity and temperature. It was found that the total oxygen transport resistance (Rtotal) increased obviously with the increase of the humidify, and the variation of Rtotal under different conditions was mainly related to the change of RPA. Combined with the phenomenon that the experimental value of RM was less than the calculated value at high humidity, but higher than that at high operation temperature, we speculate that the cause of that RPA increased obviously at high humidity is the occupancy or blockage of gas phase transport channel in catalyst layer (CL) by phosphoric acid due to the water absorption of phosphoric acid in CL and the swelling of membrane. This consequence indicates that it is the change of phosphoric acid distribution that dominateCis the Rtotal at high humidity.