Fuel Cells

A fuel cell is an electrochemical cell that converts energy from a fuel into electrical energy. Electricity is generated from the reaction between a fuel supply and an oxidizing agent. The reactants flow into the cell, and the reation products flow out of it, while the electrolyte remains within it. Fuel cells can operate continuously as long as the necessary reactant and oxidant flows are maintained.


1. Micro-DMFC

The micro-DMFC (Direct-Methanol fuel cell) employ methanol and water to produce energys, which follows the following chemical reaction:


Since the energy density of methanol is very high (10 times larger than lithium), the energy density of micro-DMFC is much more higher than the traditional fuel cells. Besides, the reaction products are just water and carbon dioxide, which makes micro-DMFC environment friendly.

To anode mold of micro-DMFC is fabricated by photolighographe and the cathode mold of micro-DMFC is fabricated by machine. Then hot embossing is used to fabricate bipolar plates by the anode and cathode mold. To improve the hydrophilicity of surface, three bi-layers of PDDA and PSS are self-assembled on the plates.Gas separation is made of a piece of carbon paper coated with PTFE.

The micro-DMFC is assembled following the structure in figure 1 (right). Membrane electrode assembles with sealant and the bipolar plates are sandwitched one by one with bipolar plates as the end plates. Each fuel cell is serial interconnected by the bipolar plates. The stack can be extended to more than two fuel cells serial interconnected. Ambient air could diffuse to cathode catalyst thtough the gap constructed by a pillar array. The final fuel cells are as shown in figure 1 (right).


Fig 1. Structure of micro-DMFC stack (left) and a single micro-DMFC stack (right)