A-Na molecule ©
MIPT
(December 30, 2015) The
ion-exchange synthetic membranes based on amphiphilic compounds are able to
convert the energy of chemical reactions into electrical current.
An international
research group including Russian, French and German scientists has developed
ion-exchange synthetic membranes based on amphiphilic compounds that are able
to convert the energy of chemical reactions into electrical current. The new
development described in the journal Physical Chemistry, Chemical Physics could
potentially be used in fuel cells, and in separation and purification
processes. The study was conducted by Moscow-based Laboratory of Functional
Organic and Hybrid Materials, which was opened in 2014.
Azo-Na © MIPT
Fuel cells consist of separate galvanic cells and their
closest relatives are batteries (primary cells) and accumulators (secondary
cells). Batteries convert the energy of the reaction between an oxidizing agent
and a reducing agent, and stop working when these agents are used up. An
accumulator is able to store electrical energy applied to it from an external
source, convert it to chemical energy, and release it again, thus reversing the
process.
Example of a fuel
cell operating on hydrogen and oxygen. It converts
chemical energy
not into heat (as would be the case if hydrogen
was burned in a
burner), but into electricity. These devices were used
on the Apollo
lunar modules, and the Space Shuttle and Buran spacecraft systems
© R.Dervisoglu /
Wikimedia
A fuel cell on the other hand, which is also an
electrochemical generator, gets the materials that it needs to function from an
external source. These materials are a reducing agent (usually hydrogen,
methanol or methane) and an oxidizing agent, oxygen. Providing these materials
from an external source means that electricity can be obtained from a fuel cell
continuously without having to stop to recharge for as long as the parts of the
cell are in working order.
Azo-Na © MIPT
The main elements of this generator are a cathode and an
anode, separated by an ion-exchange membrane.
At the cathode, the reducing agent is dissociated – an
electron is separated from a hydrogen molecule (or another fuel) and thus a
positively charged hydrogen ion, a proton, is formed. The membrane allows
protons to pass through, but retains the electrons – these particles are forced
to take the “long route” through an external circuit. Only once they have
passed through this circuit (the device that the fuel cell is powering) can
they reach the anode where they find oxygen and the protons that passed through
the membrane to combine and form water. The electrons, which are forced to go
around the membrane, create a current in the external circuit that can be
utilized.
© MIPT
Why do we need fuel
cells and why are they not used more widely?
Fuel cells use the same fuel that can be burned in
conventional internal combustion engines producing the same basic products -
water vapour in the case of hydrogen and water vapour with carbon dioxide in
the case of organic fuel. However, compared to a traditional engine, a fuel
cell has at least two advantages: first, the process takes place at a lower
temperature without a number of harmful emissions such as nitrogen oxides;
secondly, fuel cells can have a much higher level of efficiency. Petrol and
diesel generators are limited by thermodynamic laws (they do not allow an
efficiency coefficient of more than 80% for example), but such laws do not
apply to fuel cells.