Tag Archives: Oxides

Bread mold could build the batteries of the future

A study of a strain of red bread mold could revolutionize our rechargeable battery technology. The paper’s findings could be the first step towards producing sustainable electrochemical materials.

Image via ulb.ac.be, credits to Albert Goldbeter.

That yucky slimy brick-red stuff that grows on your bread (if you happen to have bread that’s a few weeks old lying around un-microwaved) might, at first sight, seem not any good to anyone. Ever. But you’d be wrong. Known as Neurospora crassa, scientists have recently shown that this fungus can take manganese from its food and tie it into mineral composites with properties that lend well to battery-making.

“We have made electrochemically active materials using a fungal manganese biomineralization process,” says Geoffrey Gadd of the University of Dundee in Scotland.

“The electrochemical properties of the carbonized fungal biomass-mineral composite were tested in a supercapacitor and a lithium-ion battery, and it [the composite] was found to have excellent electrochemical properties. This system therefore suggests a novel biotechnological method for the preparation of sustainable electrochemical materials.”

Gadd and his colleagues have worked with fungi before, studying how they transform metal and other elements’ atoms in surprising (and often very useful) ways. Their earlier work shows how fungi can be used to fixate toxic lead and uranium compounds, for example. That research had them wondering whether the fungi could offer a useful method for the preparation of novel electrochemical materials, too.

“We had the idea that the decomposition of such biomineralized carbonates into oxides might provide a novel source of metal oxides that have significant electrochemical properties,” Gadd says.

For the study, Gadd and his team incubated N. Crassa in a medium enriched in urea and manganese chloride (MnCl2). The long, branching fungal filaments (known as hyphae) became either biomineralized with or enevloped by minerals of various compositions. After heat-treating the fungus, the resulting mixture of carbonized biomass and manganese oxides were shown to have ideal electrochemical properties for use in supercapacitators (lithium-ion batteries).

“We were surprised that the prepared biomass-Mn oxide composite performed so well,” Gadd says.

Compared to other attempts to incorporate manganese oxides in lithium-ion batteries, Gadd’s biomass-mineral composite “showed an excellent cycling stability and more than 90% capacity was retained after 200 cycles,” he says.

Gadd’s team is the first to prove the effectiveness of biosynthesizing active electrode material using fungal mineralization processes. Gadd says the next step is to explore the use of fungi in producing potentially useful metal carbonates. They’re also interested in finding fungal processes for  valuable or scarce metal recovery in other chemical forms.

The full paper, titled “Fungal Biomineralization of Manganese as a Novel Source of Electrochemical Materials” has been published online in the journal Current Biology and can be read here.

First entropy-stabilized complex oxide alloy synthesized by NCSU

North Carolina State University researchers have succeeded in proving that the crystalline structure of a material can be formed by disorder at an atomic level and not chemical bonds, by creating the world’s first entropy-stabilized alloy incorporating oxides.

Schematic illustration of an entropy stabilized oxide at the atomic scale.
Image via nanowerk

“High entropy materials research has been a hot field since 2007, but no one reported that the unique structure of these materials was indeed stabilized by configurational disorder alone — and no one had created an entropy-stabilized material using anything other than metals,” says Jon-Paul Maria, a professor of material science and engineering at NC State and corresponding author of a paper on the new findings.

High entropy alloys are materials consisting of four or more distinct elements in roughly equal amounts, but distributed randomly at an atomic scale. Their remarkable properties have made them a hot topic in recent years, and only a small hurdle stood between them and fame — they didn’t naturally exist. So, presumably with a cry of “For Science!” researchers went about to make themselves some.

“While the influence of entropy is present in the natural world — for example, the arrangement of metal ions in feldspar, one of the most common minerals in Earth’s crust — crystalline solids that are stabilized by entropy alone do not exist naturally,” Maria says. “We wanted to know if it was possible to stabilize an oxide using entropy and whether we could prove it. The answer was yes to both. Oxides were chosen for this study because they enabled us to directly test this entropy question.”

First let’s take a look at exactly how atoms arrange themselves in a crystal. A crystalline structure is not random, but consists of a repeating arrangement of atoms, unique from material to material, called it’s “lattice type.” In conventional materials, the arrangement of atoms is regular and ordered, with imperfections causing structural incompatibility that can lead to the structure breaking down around it. That’s why mine flowers grow in regular, geometric shapes — they are made up of regular, geometric arrangements of atoms.

But in an entropy-stabilized material, this no longer holds true. The relative arrangement of atoms is completely random. By adding more and more different atom types to a crystal, you can generate more and more disorder if the arrangement of atoms on that lattice remains random. Finding the right mix of atoms that will retain this randomly mixed state is the key to entropy stabilization and testing the entropy question.

NCSU’s researchers forged their entropy-stabilized material out of five different oxides: magnesium oxide, cobalt oxide, nickel oxide, copper oxide and zinc oxide. These were mixed in powder form, pressed into a pellet, and kept at 1000 degrees Celsius for a few days to let them mingle.

Then they took it and used the Advanced Photon Source at Argonne National Laboratory and X-ray fluorescence spectroscopy to determine that the constituent atoms in the entropy-stabilized oxide were evenly distributed and that their placement in the crystalline lattice structure was random.

“The spectroscopy told us that each unit cell in the entropy-stabilized oxide’s structure had the appropriate distribution of atoms, but that where each atom was located in a unit cell was random,” Maria says. “Making this determination is very difficult, and requires the most sophisticated characterization tools available at the Advanced Photon Source.

“This is fascinating — we’ve proved that you can create entirely new crystalline phases of matter — but it’s fundamental research,” Maria says. “A lot of additional work needs to be done to characterize the properties of these materials and what the potential applications may be.

“However, the work does tell us that we’ll be able to engineer new materials in unusual ways — and that is very promising for developing materials with desirable properties.”