A prototype glucose battery inspired by the body’s metabolism
Researchers reporting in ACS Energy Letters have devised a battery powered by vitamin B2 (riboflavin) and glucose. Inspired by how human bodies break down glucose for energy using enzymes, the team incorporated riboflavin into a prototype flow cell battery. The riboflavin mediator helped shuttle electrons between the battery’s electrodes and the glucose electrolyte, generating an electrochemical flow from the energy stored in the sugar.
“Riboflavin and glucose flow cells can generate electricity from naturally derived energy sources,” says Jong-Hwa Shon, the study’s lead author. “Using non-toxic components that are both inexpensive and naturally abundant, this system offers a promising pathway toward safer and more affordable residential energy storage.”
A flow cell battery stores electrochemical energy in two electrolytes that flow through the system. As reactions occur in the electrolyte and at the electrodes, the stored chemical energy converts into electrical energy, and vice versa. And because most plants contain glucose, this sugar has the potential to be an abundant and low-cost electrolyte as the energy source in a flow cell battery.
Current glucose fuel cell prototypes require noble metal catalysts to break down the sugar molecules to generate power, but these models produce little power and are difficult to scale up for industrial use. Riboflavin has shown promise in other flow battery types as an alternative to metal catalysts because the vitamin is stable at the basic pH needed by electrolytes in glucose flow cells. So, Shon, Ruozhu Feng, Wei Wang and colleagues wanted to design a glucose fuel cell with riboflavin as the catalyst.
For the battery, the team used a carbon material to form the positive and negative electrodes. The electrolyte flowing around the negative electrode contained an active form of riboflavin and glucose, and at the positive electrode, the electrolyte included potassium ferricyanide or oxygen (as is used in conventional fuel cells) in a solution at a basic pH. Although the cell with potassium ferricyanide allowed the team to precisely measure riboflavin’s catalytic activity, the cell with oxygen is a more cost-effective option for large-scale, practical use.
In a demonstration with the flow cell containing potassium ferricyanide, the team observed electrons moving across the cell and a power density at room temperature comparable to that of existing flow cell batteries using vanadium metal. Contrarily, the flow cell containing oxygen had slower reactions at the electrodes than the potassium ferricyanide design. The researchers say this is likely due to oxygen breaking down riboflavin in the presence of light, which would self-discharge the battery. However, the oxygen version still demonstrated improved power density compared to the previous reports. The researchers say they plan to improve the power density of the glucose flow cell containing oxygen by preventing light reactions with riboflavin and by refining cell engineering.
The authors acknowledge funding from the Energy Storage Research Alliance (experiment, manuscript writing and revision), an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences; and by the Energy Storage Materials Initiative (ideation and initial experiment) at Pacific Northwest National Laboratory, which is a Laboratory Directed Research and Development project.
The paper can be found here.