PEM fuel cell based on PBI polymer and phosphoric acid, can be operated at temperature
between 120 and 180 °C. Reactants humidification is not required and CO content up to 2% in the fuel can be
tolerated, affecting only marginally performance. This is what makes HT PEM very attractive, as low quality
reformed hydrogen can be used and water management problems are avoided. Till nowadays, from
experimental point of view, only few studies relate to the development and characterization of high temperature
stacks. The aim of this paper is to present the main design features and the performance curves of a 25 cells HT
PEM stack based on PBI and phosphoric acid membranes. Performance curves refer to the stack operating
with two type of fuels: pure hydrogen and a gas mixture simulating a typical steam reformer output. The stack
voltage distribution analysis and the stack temperature distribution analysis suggest that cathode air could be
used as coolant leading to a better thermal