Hydrogen Peroxide and Fuel Cells
Date: Winter 2011-2012
Hello, I am a student in 10th grade and I was wondering if I could get some information about what happens when hydrogen peroxide decomposes by the use of a catalyst. Is there any transfer or release of electrons or ions during the decomposition? And if there is a release of ions and electrons could one hypothetically use this to power a fuel cell?
The decomposition of hydrogen peroxide simply results in water,
oxygen, and energy. A simple decomposition reaction. A fuel cell
requires two components, a "fuel" and an "oxidizer" that are introduced
separately at the anode and cathode (respectively) of the fuel cell, and
combine (not decompose) in a controlled reaction, generating an
external flow of electrons.
Hydrogen peroxide by itself would be of no use in a fuel cell because
all it can do is decompose. It is an oxidizing agent, to be sure, but you
will still need a separate "fuel". Further, uncontrolled decomposition of
H2O2 by exposure to a catalyst, is counterproductive, since the
decomposition will proceed within a few seconds, and the resulting
oxygen will escape, and the resulting energy will be wasted heating the
Hydrogen peroxide decomposes by the reaction: 2 H2O2 (aq) -----> O2
(gas) + 2 H2O (liq)
In the absence of a catalyst, this reaction is negligibly slow; HOWEVER, it
is catalyzed by many substances: substances in/on the skin, MnO2 to mention
just a couple.
No ions or electron transfers are required, but there are so many pathways,
some mechanisms may well involve those pathways. The problem using H2O2 to
power a fuel cell is controlling the speed of the reaction -- there would be
some "engineering" design issues. If you do a search on the term(s)
"decomposition of hydrogen peroxide", you will find a lot of information.
The motivation for all the detailed information is that 100% H2O2 is a
rocket fuel. Hydrogen peroxide comes in three concentrations that can be
stabilized -- 3% (pharmacy grade), 30% (chemical reagent grade) and 70% (be
very careful grade!!). Rocket grade (rocket fuel grade) requires special
handling and is not commonly available -- very touchy!
Click here to return to the Engineering Archives
Update: June 2012