Silver-infused bacteria build more efficient microbial fuel cells

Microbial fuel cells are a promising new technology for generating electricity, but so far they’re plagued by inefficiency. Now, researchers at UCLA have found a way to wring more energy out of them, by feeding the bacteria silver to make them more conductive.

Some bacteria produce electrons through their normal metabolic processes, and microbial fuel cells tap into that to generate electricity. Grow them in films on electrodes, feed them organic matter, and presto – you’ve got a device that generates electricity while helping clean up wastewater. At least, that’s how it would work in an ideal world, but getting a decent output has remained frustratingly elusive.

So for the new study, the UCLA team looked to ways to boost the amount of electricity generated. The researchers started with bacteria called Shewanella oneidensis, a promising fuel cell microbe that thrives in low-oxygen environments. It turns out that its efficiency is limited by the bacteria’s membranes, through which electrons have a hard time escaping.

So the researchers tackled this problem by essentially implanting transmission wires inside the bacteria. The team grew Shewanella on electrodes made of graphene oxide with silver ions embedded in it. The bacteria reduce these ions into nanoparticles that are incorporated inside their cells, which helps more electrons escape to the outside of their membranes.

“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,” says Xiangfeng Duan, corresponding author of the study.

The team says that with the enhancements, the bacteria now shuttle 81 percent of the electrons they produce into the electrode. That generates 0.66 milliwatts of power per square centimeter, which the researchers claim is the highest power density for a microbial fuel cell by quite a margin. The breakthrough could help make microbial fuel cells more practical for real-world use.

The research was published in the journal Science.

Source: UCLA

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