Fuel cell is an energy conversion device that converts the chemical energy stored in fuels (Hydrogen) and oxidants into electricity through electrochemical reaction. We work on specific type of fuel cell which is Polymer electrolyte membrane fuel cell (PEMFC), which is consists of an anode and a cathode, and a polymer electrolyte membrane (PEM) in between. At the anode, hydrogen flows into the flow channel through the gas diffusion layer (GDL) to the catalyst layer (CL). In the anode CL, hydrogen splits into protons (hydrogen ions) and electron, these electron travels through an external circuit to the cathode, thus generate electricity. At the same time, on the cathode side, air or oxygen flows through the GDL to CL, where it reacts with the protons and electrons from the anode, producing water and heat.
The production and the distribution of the water inside fuel cell must be investigated because if the amount of water inside the fuel cell is two high that will effect on the performance and the efficiency of the fuel cell, on the other hand, if the amount of water is too low that will cause dehydration the membrane, ohmic resistance of the membrane will increase, the proton transportation in side membrane will decrease, and all of them will effects on the performance and the efficiency of the fuel cell …… so the distribution of water inside the fuel cell must be balanced, so we need the investigate the water distribution inside fuel cell by using neutron imaging.
Neutron can be founded in all elements except hydrogen ….. But how we can extract it from the element?
- Nuclear reaction: hit the nucleus like U235 with α particle that will generate neutrons, krypton and barium.
- Spallation source: hit a suitable nucleus like tungsten (W) or lead (Pd) with high energy proton (1GeV).
- Accelerators based source: accelerating a charged particle using electric field which can be generated by van de graaf generator.
How we do the imaging?
The hydrocarbon compound can absorb these neutrons, and that will effect on the intensity of the neutron beam. By using a detector (or sometimes we use CCD camera this will gave us a colored image) place behind the sample (fuel cell) it will record the intensity of the transmitted neutron beam ….. And by using these data (intensity of the incident and transmitted beam and other) we can investigate the amount of water in any specific region in the fuel cell by using imageJ or octopus software.