Water distribution mapping in polymer electrolyte fuel cells using lock-in thermography

Effective water management in polymer electrolyte fuel cells (PEFCs) is essential to achieving optimal performance. Mapping the water distribution is therefore a useful tool for understanding operation and designing new components. One of the most powerful ways of visualising water distribution is through neutron imaging. However, this has limitations in terms of expense, accessibility and the ability to conduct representative operando experiments in a neutron beam line. Here, a simple, cost-effective, lab-based, non-invasive water visualisation tool is presented that allows the effect of operating conditions to be assessed in operando. The approach applies lock-in thermography, whereby a controlled sinusoidal heat pulse on one side of a fuel cell (here using a printed circuit board arrangement), is applied using a Peltier device, and the temperature perturbation on the other side of the fuel cell is monitored using a thermal imaging camera. By 'locking in' to the frequency of the imposed heat stimulus, it is possible to observe water build-up within the cell by monitoring the phase shift between heat pulse and measured temperature. This work validates the use of the lock-in thermography technique by mapping the water distribution under different current densities and under dry and humidified conditions.