Chapter 3E - Fuel Cells

Electrochemical cell that continuously converts chemical energy into electrical energy via a redox reaction

• material with many holes (pores) used in a fuel cell to maximise the ability of gaseous reactants to come into contact with the electrolyte

• type of galvanic cell where reactants (fuel/oxygen) are continually supplied • overal reaction always indirect combustion reaction • fuel always undergoes oxidation at anode • more efficient than power stations at converting chemical energy to electricity (40-60% vs 30-26%)

• convert chemical energy to electrical energy • anode & cathode seperated • electrons flow from anode to cathode in external circuit • electrolyte - allows for flow of ions • produces an electrode potential • connected to a load - anything consuming electrical energy • can be stacked (multiple cells connected in a series) to provide greater voltage output

• reactants are continually supplied from an external source • do not go flat/need recharging • operate in open systems & usually involve gaseous reactants • membranes are often used as electrolytes • electrodes are porous in nature

• consist of a polymer layer that conducts H⁺ ions • proton electrolyte membrane (PEM) • not aqueous

• improves contact b/w gaseous reactants & electrolyte • size of pores can vary to only allow desired molecules to pass through • increases surface area & allows for catalyst use (increased reaction rate & efficiency)

• around 80 degrees

• lower emissions of harmful sulfur & nitrogen-containing compounds • low maintenance/running costs • quiet • no direct carbon dioxide emission from H cells • much greater energy efficiency

• storage/safety issues w/ explosive hydrogen fuel • expensive to manufacture • requires new infrastructure for hydrogen fuel • hydrogen fuel generally only produced via electrolysis of water • potentially not as efficient/convient as batteries