Abstract
In this paper, the effects of operating backpressure on PEM fuel cell performance were studied at 70 ºC, 100% RH, and backpressures ranging from 1.00 to 3.04 atm. AC impedance spectroscopy and cyclic voltammetry were employed to diagnose the backpressure effects. It was observed that increasing operating backpressure could improve fuel cell performance by enhancing the fuel cell thermodynamics, increasing the exchange current densities of the reactions, accelerating the electrode kinetics, and improving the mass transfer process. However, some negative effects, such as increased H2 crossover rate and membrane resistance, were also observed.