A segmented fuel cell unit with functionally graded distributions of platinum loading and operating temperature

Desired electrochemical reaction and mass transport rates vary in the operation of PEM fuel cells due to the inhomogeneous spatial distribution of reactants and products. A segmented fuel cell unit was manufactured and a comprehensive model was developed to study the effect of the graded distributions of platinum loading and operating temperature, to simultaneously save the usage of platinum, improve the cell performance and maintain the homogeneity of current density. The increase of temperature towards the cathode outlet improved the reaction kinetics and reduced the liquid water content along the gas flow direction, which decreased the required platinum loading. A large temperature gradient may lead to membrane/ionomer dehydration and oxygen starvation near the cathode outlet due to the increase in the saturation pressure of vapor and the dilution of the increased vapor content. A systematical design of the gradients of platinum loading and temperature achieved an improved cell performance and saved the usage of Pt-based catalysts without worsening the homogeneity of current density.