In situ approach for current distribution measurement in fuel cells

In this paper, a new, simple method for measuring the current density distribution in fuel cells with meander flow fields is described. This method has been used to investigate the reactant activity along the meander channel. The corresponding experimental hardware is very simple, cost-effective and easy to integrate into the fuel cells. A thin semi-segmented plate made of expanded graphite serves as a passive resistor network. The set-up is based on the idea that the electronic conductivity of the expanded graphite is relatively low in current direction. For typical current densities in polymer electrolyte fuel cell (PEFC), this leads to voltage drops in the range of several millivolts using usual current densities. On the other hand, the conductivity in-plane is considerable higher which is beneficial for equalizing the potential across the segment area. The new set-up can be used to measure the current density distribution in a single cell as well as in a stack at any desired position. The local potential difference across the graphite plate is caused by the local current flowing through it. By mapping these potential differences at different locations, the current distribution in the fuel cell can be derived. This experimental set-up has been used to investigate the current distribution of a 240 cm2 PEFC single cell with different operating conditions. The real-time current density distributions measured by the present method are described in this paper.