Environmental Engineering Reference
In-Depth Information
DID YOU KNOW?
Hydrogen fuel cell vehicles (FCVs) emit approximately the same amount
of water per mile as vehicles using gasoline-powered internal combustion
engines (ICEs).
A hydrogen fuel cell is a device that uses hydrogen (or hydrogen-rich fuel) and
oxygen to create electricity through an electrochemical process. A single fuel cell
consists of an electrolyte and two catalyst-coated electrodes (a porous anode and a
cathode). The various types of fuel cells all work similarly:
•
Hydrogen (or hydrogen-rich fuel) is fed to an anode, where a catalyst sepa-
rates the negatively charged hydrogen electrons from positively charged
ions.
•
At the cathode, oxygen combines with electrons and, in some cases, with
species such as protons or water, resulting in water or hydroxide ions,
resp e ct ively.
•
For polymer electrolyte membrane and phosphoric acid fuel cells, protons
move through the electrolyte to the cathode, where they combine with oxy-
gen and electrons to produce water and heat.
•
For alkaline, molten carbonate, and solid oxide fuel cells, negative ions
travel through the electrolyte to the anode, where they combine with hydro-
gen to generate water and electrons.
•
The electrons from the anode cannot pass through the electrolyte to the
positively charged cathode; they must travel around it via an electrical cir-
cuit to reach the other side of the cell. This movement of electrons is an
electrical current.
ENVIRONMENTAL IMPACTS OF FUEL CELLS
Beyond the expectation that hydrogen leakage from its use in fuel cells could greatly
impact the hydrogen cycle and could, when oxidized in the stratosphere, cool the
stratosphere and create more clouds, delaying the break up of the polar vortex at
the poles and making the holes in the ozone layer larger and longer lasting, little is
understood about how hydrogen leakage would affect the environment. For example,
much uncertainty exists over the extent of the impact of hydrogen emissions on soil
absorption of hydrogen from the atmosphere. This concept is important because if
we use extensive quantities of hydrogen for fuel cells, absorption of hydrogen by soils
could have a compensatory effect on any possible anthropogenic emissions. Again,
it is important to emphasize that little is understood about how hydrogen leakage
would affect the environment.
