An engineering team at Washington University in St. Louis, Missouri has developed a new method to look at the rate of oxidation (or central breakdown) in fuel cells, which could revolutionize battery-powered devices, such as laptops, cell phones, and automobiles.
Fuel cells generate electricity by typically using hydrogen as fuel and air as an oxidant, so they are cleaner forms of energy.
Every fuel cell has an electrolyte, which carries electrically charged particles from one electrode to another, and a catalyst to speed up the reactions of the electrodes. The electrolyte plays an important role in allowing the appropriate ions to pass through and ultimately provide the proper chemical reaction.
“If you buy a device — a car, a cell phone — you want it to last as long as possible,” said Vijay Ramani, the Roma B. and Raymond H. Wittcoff Distinguished Professor of Environment & Energy at the university’s School of Engineering & Applied Science, in a statement.
The problem is, the lifetime and success of a fuel cell is affected by the oxidation, or breakdown, of its central electrolyte membrane, which can lead to a formation of holes in the membrane and cause a chemical short-circuit.
To address this drawback, the researchers use fluorescence spectroscopy inside the fuel cell to see the formation of chemicals, namely free radicals, that are responsible for the oxidation of the electrolyte membrane and provide potential solutions to the problem.
“Fluorescence spectroscopy is based on the innate ability of certain molecules (fluorescent probes) to absorb light of a particular wavelength, and after a short amount of time, emit light in a series of different wavelengths constituting that molecules unique emission spectrum,” said Ramani.
These molecules are very delicate, and some are extremely sensitive to highly reactive free radicals. When they interact with the free radical, their fluorescence intensity decreases at a rate proportional to the rate of molecular interaction with the radical. Therefore, this rate of decrease informs the researchers of the concentration of free radicals in the test system, allowing them to quantify the free radicals responsible for oxidation.
“Since the free radicals that cause the fuel cell membrane degradation are so short-lived, and the anion exchange membranes are so thin, our novel in situ approach is key to better study, understand and prevent the chemical breakdowns that is occurring during fuel cell operation,” Javier Parrondo, a postdoctoral researcher and research co-author, said in a statement.
In the next few months, the researchers plan on introducing antioxidant chemicals inside alkaline fuel cell membranes to see if they can reduce the rate at which the membranes break down.
“This work provides us with an in-depth understanding of the rate of generation of superoxide anion radicals and other alkali-compatible ROS (reactive oxygen species) in operating alkaline polymer electrolyte fuel cell,” said Ramani. “This understanding will allow us to design suitable mitigation strategies that will enhance the lifetime of anion exchange membrane separators by preventing their oxidative degradation.”
The paper is published in ChemSusChem.
The research team also includes Yunzhu Zhang, a doctoral candidate in Ramani’s lab and research co-author, and Shrihari Sankarasubramanian, a doctoral researcher.
