Fuel Cell Runs on Biomass, Sunlight

Switchgrass can be fuel for a new low-temperature solar-activated fuel cell. Photo: NU/IANR

Researchers at the Georgia Institute of Technology have developed a new type of low-temperature fuel cell that directly converts biomass to electricity with assistance from a catalyst activated by solar or thermal energy.

The hybrid fuel cell can use a wide variety of biomass sources, including starch, cellulose, lignin, switchgrass, powdered wood, algae and waste from poultry processing. The device could generate power wherever significant quantities of biomass are available.

“We have developed a new method that can handle the biomass at room temperature, and the type of biomass that can be used is not restricted — the process can handle nearly any type of biomass,” said Yulin Deng, a professor in Georgia Tech’s School of Chemical and Biomolecular Engineering and the Institute of Paper Science and Technology.

Carbon-carbon bonds in biomass cannot easily be broken down by conventional catalysts, Deng noted. Microbial fuel cells yield limited power, need specific enzymes for each form of fuel — and the process is often interrupted by impurities or temperature variations.

Deng’s team altered the chemistry to allow an outside energy source to activate the fuel cell’s oxidation-reduction reaction. They grind biomass and mix it with a polyoxo-metalate (POM) catalyst in solution, then expose it to heat or sunlight. POM functions as both an oxidizer and a charge carrier, delivering electrons to the anode. The electrons are then transported to the cathode, where they are oxidized by oxygen through an external circuit to produce electricity.

The system can use soluble biomass, or organic materials suspended in a liquid. In experiments, the fuel cell operated for as long as 20 hours, indicating that the POM catalyst can be reused without further treatment. The team reported a maximum power density of 0.72 milliwatts per square centimeter, nearly 100 times higher than cellulose-based microbial fuel cells. Deng believes the output can be increased five to 10 times when the process is optimized. “I believe this type of fuel cell could have an energy output similar to that of methanol fuel cells in the future,” he said.

The new solar-induced direct biomass-to-electricity hybrid fuel cell was described Feb. 7 in the journal Nature Communications. In addition to Deng, the research team included Wei Liu, Wei Mu, Mengjie Liu, Xiaodan Zhang and Hongli Cai, all from the School of Chemical and Bio- molecular Engineering or the Institute of Paper Science and Technology at Georgia Tech.

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