Battery & Electrification Technology - November/December 2024 - 25

largely influenced by the composition of the
etching baths used to clean the electrodes
extracted from lithium-ion batteries.
" For potential future applications, the
crucial finding is that, based on data
gathered from our experiments using a
rotating electrode, we were able to determine
the number of electrons involved
in the reduction of a single oxygen
molecule. The electrochemical reduction
of oxygen can occur with either
four or two electrons. In the case of four
electrons, water is produced, but with
two electrons, we obtain the desired hydrogen
peroxide. In all the samples we
tested, we observed the two-electron
reduction, " said Dr. Warczak.
To eliminate the potential impact of
the glassy carbon electrode used as a
substrate on the results, the measurements
were repeated in systems where
individual battery powders were suspended
between two immiscible liquids.
The organic liquid contained decamethylferrocene,
a compound that donates
electrons in the oxygen reduction reaction.
The oxygen reduction occurred
spontaneously at the interface between
the liquids. These studies confirmed
that,
like the experiments with the
glassy carbon electrode, all samples catalyzed
the oxygen reduction reaction to
produce hydrogen peroxide. The concentrations
of hydrogen peroxide at the interface,
measured using a scanning electrochemical
microscope, were one to
two orders of magnitude higher than in
systems without battery waste.
" Lithium-ion batteries have generally
been viewed as just a secondary source of
carbon materials, mainly graphite, and
metals like lithium, cobalt, or nickel. Our
group's findings clearly demonstrate that
battery waste can catalyze the reduction
of oxygen to hydrogen peroxide, and in
the future, this could lead to its use in
producing this important chemical compound, "
said Dr. Warczak.
Hydrogen peroxide at a 3 percent concentration
is sold in pharmacies as a
disinfectant for wounds and inflammation,
though its effectiveness for wound
care is debatable. Solutions with concentrations
of up to 15 percent are used as
bleaches in household cleaning products
and cosmetics, such as hair lighteners. A
solution with around 30 percent concentration,
is crucial in various industries,
including chemical manufacturing (for
peroxide synthesis and as an oxidant),
pulp and paper and textiles (as a bleach),
rubber (as a raw material), electronics
and metal (as an etching agent), and food
processing (as a biocidal substance).
Interestingly, hydrogen peroxide can also
serve as an oxidizer for fuels, including
rocket fuels. It first played this role in the
1940s, when it was used in the early rockets
capable of crossing the conventional
boundary of space. However, at that time, its
concentrations did not exceed 80 percent,
and technological limitations hindered
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Battery & Electrification Technology - November/December 2024

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