Experimental study of variable operating parameters effects on overall PEMFC performance and spatial performance distribution

Back pressure, relative humidity and air stoichiometry, these operational parameters have a crucial influence on the performance of PEMFC. Overall performance, stability and homogeneity of spatial performance distribution under variable operating parameters are in this paper researched. Polarization curves and Electrochemical Impedance Spectroscopy (EIS) are utilized to show the overall performance and resistance losses of PEMFC at variable operating parameters, while the segmented cell technique can provide real-time spatial current density distribution to reflect the uniformity and stability of the performance. Higher back pressure is an effective approach to improve the overall performance of the fuel cell whereas the uniformity keeps constant and the local stability decreases. The back pressure should be limited to some extent (0.3 bar in this paper). With the relative humidity increasing to a value (70% in this paper), overall performance and current distribution homogeneity of PEMFC enhance, but the stability sustains. Under higher air stoichiometry the fuel cell shows better overall and local performance, current distribution homogeneity and local stability. It's found that in all cases the performance near the outlet parts are worst due to poor water management and low gas concentration which could not be effectively enhanced by optimization of these operating conditions.