DeMi Cell represents principles
of action of the so-called regenerative fuel cells (RFC). This type
is considered as very promising as it combines the functions of
electrolyzers and fuel cells. When supply with external electric
power, the device works as an electrolyzer splitting water into
gaseous hydrogen and oxygen. In reverse, when feed the anode and
cathode with hydrogen and oxygen, respectively, a spontaneous
electrochemical reaction takes place, which chemical product is only
water, but also electricity and heat are generated.
This dual action of regenerative fuel cells is
possible due to the use of bi-functional electrocatalysts, which
accelerate in a reversible manner the electrochemical conversion of
hydrogen and oxygen.
Although our prototype does not contain noble
metal electrocatalysts, as the real systems do, it is able to work
consequently as an electrolyzer and fuel cell, thus demonstrating
the principles of action of regenerative fuel cells.
In addition, our model possesses also the function
of gas-holders that store the gases generated during electrolysis
till the subsequent operation as a fuel cell.
Thus, in reality, you may operate with several
devices – an electrolyzer, hydrogen and oxygen gas-holders and a
fuel cell, collected in one module.
DeMi Cell prototype is
constructed applying the following criteria:
- all used materials and reacting agents to
meet as much as possible the safety working requirements and to be
environmentally friendly; thus, on one hand, the model could be used
by secondary and university students without any hazards to their
health, and on the other hand, in a case of accident there is not
going to be any leakage of poisonous or dangerous substances;
- the design of the device to be
comparatively easy for implementation and to ensure good observation
possibilities of the occurring phenomena and processes.
DeMi Cell consists of two
removable parts – transparent body and lid, on which two electrodes
with separators and connectors are assembled. The transparent body
is filled with aqueous solution of non-toxic and non-hazardous
oxygen-containing salt (sodium bicarbonate, for example), in which
both electrodes are immersed. The electrodes are made of a metal
mesh used as a current collector and non-precious metal catalysts.
They are put in special bags that serve as separators and
gas-holders at the same time. The oxygen and hydrogen, needed for
the fuel cell’s operation, are obtained inside the cells through
water electrolysis, carried out via supplying external voltage out
of a proper photovoltaic element (LeXsolar solar module) or an
ordinary 9V battery. Thus, the model can be used both for
demonstrating principles of operation of electrolyzers, powered by
solar energy, and fuel cells. The prepared in that manner fuel cell
ensures powering up small electronic devices, such as light emitting
diodes (LEDs), digital displays, etc.
Several cells can be connected in series thus
obtaining higher voltage (proportional to the number of cells) and
demonstrating the principle of stacking used in the real fuel cell
DeMi Cell can be used both for
demonstrations and labs performed by
Stack 1 of three connected in series DeMi Cells 2
operating as a fuel cell supplying a load 8 (solid contour) or as an
electrolyzer (dashed contour) charged by an external power supplier
7: 3- transparent body, 4- electrolyte, 5- electrodes, 6- separators