Researchers infuse bacteria with silver to improve power efficiency in
fuel cells

Date:
September 16, 2021
Source:
University of California - Los Angeles
Summary:
A team of engineers and chemists has taken a major step forward
in the development of microbial fuel cells -- a technology that
utilizes natural bacteria to extract electrons from organic matter
in wastewater to generate electrical currents.



FULL STORY ========================================================================== A UCLA-led team of engineers and chemists has taken
a major step forward in the development of microbial fuel
cells -- a technology that utilizes natural bacteria to
extract electrons from organic matter in wastewater to generate electrical currents. A study detailing the breakthrough was recently published in Science. 

========================================================================== "Living energy-recovery systems utilizing bacteria found in
wastewater offer a one-two punch for environmental sustainability efforts," said co- corresponding author Yu Huang, a professor
and chair of the Materials Science and Engineering Department at the UCLA Samueli School of Engineering. "The natural
populations of bacteria can help decontaminate groundwater by breaking
down harmful chemical compounds. Now, our research also shows a
practical way to harness renewable energy from this process." 
The team focused on the bacteria genus Shewanella,
which have been widely studied for their
energy-generation capabilities. They can grow and thrive
in all types of environments -- including soil, wastewater and
seawater -- regardless of oxygen levels.   Shewanella species naturally break down organic waste matter into
smaller molecules, with electrons being a byproduct of
the metabolic process. When the bacteria grow as films
on electrodes, some of the electrons can be captured,
forming a microbial fuel cell that produces electricity. 
However, microbial fuel cells powered by Shewanella oneidensis
have previously not captured enough currents from the bacteria to make the technology practical for industrial
use. Few electrons could move quickly enough to escape the
bacteria's membranes and enter the electrodes to provide sufficient
electrical currents and power.

To address this issue, the researchers added nanoparticles of
silver to electrodes that are composed of a type of graphene
oxide. The nanoparticles release silver ions, which bacteria reduce
to silver nanoparticles using electrons generated from their metabolic
process and then incorporate into their cells. Once inside the bacteria, the silver particles act as microscopic transmission
wires, capturing more electrons produced by the bacteria.

"Adding the silver nanoparticles into the
bacteria is like creating a dedicated express lane for electrons, which enabled us to extract more electrons
and at faster speeds," said Xiangfeng Duan, the
study's other corresponding author and a professor of chemistry and biochemistry at UCLA.  With greatly improved electron transport efficiency, the resulting silver- infused Shewanellafilm outputs more
than 80% of the metabolic electrons to external circuit, generating
a power of 0.66 milliwatts per square centimeter - - more than double the previous best for microbial-based fuel cells.

With the increased current and improved efficiencies, the study, which
was supported by the Office of Naval Research, showed that fuel cells
powered by silver-Shewanella hybrid bacteria may pave
the way for sufficient power output in practical settings.

Bocheng Cao, a UCLA doctoral student advised by both Huang
and Duan, is the first author of the paper. Other UCLA senior
authors are Gerard Wong, a professor of bioengineering;
Paul Weiss, a UC Presidential Chair and distinguished professor of
chemistry and biochemistry, bioengineering, and materials science and engineering; and Chong Liu, an assistant professor of chemistry and biochemistry. Kenneth Nealson, a professor emeritus of earth
sciences at USC, is also a senior author.

========================================================================== Story Source: Materials provided by
University_of_California_-_Los_Angeles. Note: Content may be edited for
style and length.


========================================================================== Journal Reference:
1. Bocheng Cao, Zipeng Zhao, Lele Peng, Hui-Ying Shiu, Mengning
Ding, Frank
Song, Xun Guan, Calvin K. Lee, Jin Huang, Dan Zhu, Xiaoyang Fu,
Gerard C.

L. Wong, Chong Liu, Kenneth Nealson, Paul S. Weiss, Xiangfeng Duan,
Yu Huang. Silver nanoparticles boost charge-extraction efficiency
in Shewanella microbial fuel cells. Science, 2021; 373 (6561):
1336 DOI: 10.1126/science.abf3427 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/09/210916142846.htm

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