Rock Breathing Bacteria May Lead to Bio-Batteries, Fuel Cells and Uranium Clean Up

A discovery by scientists at the University of East Anglia could contribute to the development of systems that use domestic or agricultural waste to generate clean electricity.

Image Credit: University of East Anglia

Published by the leading scientific journal, Proceedings of the National Academy of Sciences (PNAS), the researchers have demonstrated for the first time the mechanism by which some bacteria survive by ‘breathing rocks’.

The findings could be applied to help in the development of new microbe-based technologies such as fuel cells, or ‘bio-batteries’, powered by animal or human waste, and agents to clean up areas polluted by oil or uranium.

“This is an exciting advance in our understanding of bacterial processes in the Earth’s sub-surfaces,” said Prof David Richardson, of UEA’s School of Biological Sciences, who is leading the project.

“It will also have important biotechnological impacts. There is potential for these rock-breathing bacteria to be used to clean-up environments contaminated with toxic organic pollutants such as oil or radioactive metals such as uranium. Use of these bacteria in microbial fuel-cells powered by sewerage or cow manure is also being explored.”

The vast proportion of the world’s habitable environments is populated by micro-organisms which, unlike humans, can survive without oxygen. Some of these micro-organisms are bacteria living deep in the Earth’s subsurface and surviving by ‘breathing rocks’ – especially minerals of iron.

Iron respiration is one of the most common respiratory processes in oxygen-free habitats and therefore has wide environmental significance.

Prof Richardson said: “We discovered that the bacteria can construct tiny biological wires that extend through the cell walls and allow the organism to directly contact, and conduct electrons to, a mineral. This means that the bacteria can release electrical charge from inside the cell into the mineral, much like the earth wire on a household plug.”

‘Characterization of an electron conduit between bacteria and the extracellular environment’ by R Hartshorne (UEA), C Reardon (Pacific Northwest National Laboratory), D Ross (Pennsylvania State University), J Nuester (Pennsylvania State University), T Clarke (UEA), A Gates (UEA), P Mills (UEA), J Fredrickson (Pacific Northwest National Laboratory), J Zachara (Pacific Northwest National Laboratory), L Shi (Pacific Northwest National Laboratory), A Beliaev (Pacific Northwest National Laboratory), M Marshall (Pacific Northwest National Laboratory), M Tien (Pennsylvania State University), S Brantley (Pennsylvania State University), J Butt (UEA) and D Richardson (UEA) is published on December 14 in the online early edition of PNAS.

Samsung SDI Direct Methanol Fuel Cell Achieves Higher Power with Inorganic Nanoparticles

FIG. 1 illustrates the impregnation of inorganic conductive nano-particles into a micro-channel and between polymer backbones of an ionic conductive polymer  used for direct methanol fuel cells according to Samsung scientists. 

Samsung SDI Co., Ltd. (Suwon-Si, Gyeonggi-Do, KR) developed a polymer electrolyte for direct methanol fuel cells that shows higher power thanks to nanoparticles. The electrolyte includes an ionic conductive polymer membrane; a porous support having nano-sized pores; and inorganic conductive nanoparticles including an ionic conductive material impregnated into the porous support. The inorganic conductive nano-particles are impregnated into microchannels formed by aggregation of polar portions of the ionic conductive polymer membrane, and/or between polymer backbones of the ionic conductive polymer membrane, according to inventors Hae-kyoung Kim and Ju-hee Cho in United States Patent 7,625,651.

The amount of porous support comprises 50-300 parts by weight based on 100 parts by weight of the inorganic conductive nano-particles. The ionic conductive nanoparticles used is in the range of 3-90 parts by weight based on 100 parts by weight the polymer electrolyte, and a mixed weight ratio of the porous support and the ionic conductive material is 1:9 to 9:1, and the ionic conductive polymer membrane comprises at least one ionic conductive polymer selected from the group consisting of a 4-fluorinated sulfonated polymer and a benzene sulfonated polymer membrane having a benzene ring; wherein the inorganic conductive nano-particles have a size of from about 0.1 to about 50 nm; and wherein the ionic conductive polymer membrane has a thickness of from 30 to 200 microns.

Inorganic nanoparticles include boron (B), aluminum (Al), gallium (Ga), tin (Sn), phosphorous (P), antimony (Sb), tellurium (Te), iodine (I), and transition metals.  Transition nanometals include tungsten (W), molybdenum (Mo), phosphorous (P), silicon (Si), cobalt (Co), cesium (Cs), vanadium (V), and nickel (Ni).

The polymer electrolyte is made using  the heteropoly acid of formula (1) comprises:  tungsto (VI) phosphoric acid, silicotungsto (VI) phosphoric acid, tungstosilicic acid, cesium hydrogen tungstosilicate, molybdophosphoric acid, molybdosilicic acid, ammonium molybdodiphosphate, sodium molybdophosphate, potassium tungstophosphate, or potassium molybdodivanado phosphate

The polymer electrolyte inorganic conductive nano-particles are impregnated into an ionic conductive polymer membrane by: soaking an ionic conductive polymer membrane in a solvent; adding a heteropoly acid to the ionic conductive polymer membrane in the solvent to form a mixture; and mixing a precursor of a porous support with the mixture, wherein by mixing the heteropoly acid and the precursor, the heteropoly acid and the precursor react to form inorganic conductive nano-particles within at least one selected from the group of microchannels formed by aggregation of polar portions of the ionic conductive polymer membrane, and between polymer backbones of the ionic conductive polymer membrane, thus impregnating the ionic conductive polymer membrane with inorganic conductive nano-particles.

The polymer electrolyte  inorganic conductive nano-particles are further formed by: dispersing a surfactant into the solvent prior to soaking the ionic conductive polymer membrane in the solvent to form the first solution; and neutralizing the mixture with alkali prior to mixing the precursor of the porous support with the mixture.

FIG. 2 is a graph of ionic conductivity of a polymer electrolyte manufactured by Samsung;

FIG. 3 is a graph of a change in cell potential with respect to current density and nanoparticles used in direct methanol fuel cells (DMFCs) manufactured by the Samsung scientists.

 

Fuel Cells, Hydrogen Energy and Related Nanotechnology – A Global Industry and Market Analysis, a new report by iRAP takes an in-depth look at the use of nanomaterials by the fuel cell industry.  The report notes more than 3,800 companies worldwide involved in the manufacturing chain for fuel cells, which contain hundreds of parts to make the system work.  Nanomaterials can make up 10% to 25% of the cost of a fuel cell.