Hybrid Battery Stores Electricity and Produces Valuable Chemicals at the Same Time
Rechargeable batteries store electricity in their electrode
materials, while redox flow batteries use chemicals stored in tanks
attached to the electrodes. Researchers have now developed a battery
system based on a hybrid cell, which not only stores and provides
electricity but also produces valuable chemicals in a flow system.
During operation, the furfural–nickel hydroxide battery converts
biomass-derived molecular furfural into either furfuryl alcohol or
furoic acid.
© Wiley-VCH, re-use with credit to 'Angewandte Chemie' and a link to the original article.
Furfural is a small molecule formed from pentose sugars common in
agricultural biomass, and it is considered an important platform
chemical from which a number of intermediates can be obtained for
various applications. It can be oxidized to furoic acid, a food
preservative and intermediate in the synthesis of pharmaceuticals and
fragrances. When reduced, furfural is converted into furfuryl alcohol, a
precursor in resins, flavors, and drugs. Haohong Duan and a team of
researchers from Tsinghua University in Beijing, China, have now
succeeded in obtaining both value-added chemicals during the operation
of a hybrid flow battery, increasing the cost efficiency of the battery
system.
When charged, standard rechargeable batteries store electricity in
their electrodes and feed it into a circuit as they discharge. Another
battery type, redox flow batteries, store electricity in chemicals, with
the chemical products cycling between two states and remaining within
the battery. Combining both concepts, the researchers investigated the
extent to which such batteries are able to produce extra chemicals while
storing or providing energy.
A breakthrough came in the form of a bifunctional metal catalyst for
the anode. Made of a rhodium–copper single-atom alloy, this catalyst
smoothly converted electrolyte-containing furfural into furfuryl alcohol
when the battery was charged, while furoic acid was formed as the
battery was discharged. For the cathode, the researchers identified a
cobalt-doped nickel hydroxide material, similar to cathode materials
used in traditional nickel–zinc or nickel–metal hydride batteries.
This assembly led to a true dual-use battery system: after charging
(using a solar cell), four series-connected hybrid batteries were able
to run various devices, including LED lights and smart phones, while
continually producing furfuryl alcohol and furoic acid during battery
cycling, with these chemicals being conducted away using a flow system.
The authors found that the new hybrid battery is comparable to a
number of common batteries in terms of energy density and power density,
but it provides both power and value-added chemicals at the same time.
While storing 1 kWh of energy, 0.7 kg of furfuryl alcohol is produced,
and 1 kg of furoic acid is produced when the system provides a power of
0.5 kWh (on which a refrigerator can run for a couple of hours).
However, furfural is continually fed into the system and the products
must be separated from the electrolyte.
The team’s hybrid concept is a step toward improving the
sustainability and cost effectiveness of rechargeable batteries, but
there is still a need to develop the concept further.
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About the Author
Haohong Duan, PhD,
is an Associate Professor and doctoral Supervisor at the Department of
Chemistry, Tsinghua University, Beijing, China. His research group
develops novel electrocatalytic and photoelectrocatalytic reactions for
materials synthesis driven by renewable sources, with an emphasis on
hydrogen production, biomass conversion, plastic upcycling, and organic
synthesis.