FUEL CELLS: A BRIEF INTRODUCTION
What is a Fuel-Cell
A fuel cell is an electrochemical device (uses electrochemical reactions) to produce energy. The most common type of fuel cell uses hydrogen and oxygen as the fuel to produce energy. In this hydrogen-based fuel cell, hydrogen at the anode is oxidized to protons which are conducted through the electrolyte to the cathode. At the cathode, molecular oxygen is reduced and combined with the transported protons to form water (Figure 1). This overall process also produces electrical energy which could be used to run an electric motor in an automobile (for example).
Figure 1.
Schematics of proton exchange membrane (PEM) based
The electrolyte material (the stuff that transports the protons from one electrode to the other) can be a number of different types of material, but our research deals only with proton-exchange membranes (because they are polymers and I am a polymer chemist).
SO WHY DO I CARE?
Fuel cells may play an important part in helping to transform our society form one based on a fossil fuel economy to one based on renewable and more environmentally friendly sources. One specific scenario is referred to as the hydrogen economy. In this economy, hydrogen is produced by a renewable energy source such as solar or geothermal, then used as fuel for transportation and stationary applications. Most hydrogen is made by the steam reforming of natural gas, but this does not represent a renewable source. Other methods, such as the thermal cracking of hydrocarbons or the reaction of steam with carbon at high temperature suffer from the same problem. The best source of renewable hydrogen is from the splitting of water by electrolysis. This process produces pure hydrogen, which can be used as a fuel, and oxygen, which is released into the environment. When hydrogen is used to produce energy by combining with oxygen in a fuel cell, the only byproduct is water. This represents a completely renewable system (Figure 2).
Figure 2. Schematic of a fully renewable hydrogen economy.
This
scenario is highly idealic and a long way from being a reality, but in the short
term fuel cells may begin to provide a more efficient and more environmentally
friendly alternative to the internal combustion engine. Most (if not all)
major automobile manufacturers have a fuel-cell based vehicle under development,
and some should have production models ready for sale in the next several years.