It is becoming more urgent to find clean energy alternatives to using fossil fuels because atmospheric carbon dioxide levels are at record highs. The fact that expensive metal catalysts like platinum are required in fuel-cell technology to convert hydrogen into energy is one challenge faced by researchers.
Charles Machan (left) and Michael Hilinski (right) have identified an organic molecule that could replace the use of rare and expensive metals in fuel cells. Image Credit: College and Graduate School of Arts & Sciences, University of Virginia.
A team of researchers from the University of Virginia's College and Graduate School of Arts & Sciences has discovered an organic molecule that could substitute more expensive metal catalysts.
Fuel cells, essential for powering electric vehicles and industrial and residential generators, rely on metals such as platinum to initiate the chemical reaction that divides fuel sources like hydrogen gas into protons and electrons, subsequently converting them into electricity.
As the organic catalysts decompose into useless parts during the catalysis process, they were not considered a viable alternative to rare-metal catalysts.
However, Ph.D. Candidates Emma Cook and Anna Davis, along with Associate Professors of Chemistry Charles Machan and Michael Hilinski, discovered an organic molecule made of carbon, hydrogen, nitrogen, and fluorine that may serve as a workable substitute in a study that was published in the Journal of the American Chemical Society.
According to Machan, the molecule can start the reaction that reduces oxygen inside the fuel cell, react with the reaction’s byproducts, and return to its original state.
These molecules are stable under conditions in which most molecules degrade, and they continue to achieve activity that matches the level of transition-metal catalysts.
Charles Machan, Associate Professor, College and Graduate School of Arts & Sciences, University of Virginia
The team’s preliminary findings represent a major advancement in the hunt for cost-effective and environmentally friendly fuel cells that employ less expensive and more sustainable materials. The next generation of fuel cells may be developed in the next 5 to 10 years.
This molecule itself may not make it into a fuel cell. What this finding says is that there can be carbon-based catalytic materials, and if you modify those with certain chemical groups you can hope to turn them into great catalysts for the oxygen reduction reaction. The eventual goal is to integrate the properties that make this molecule so stable into a bulk material, in order to supplant the use of platinum.
Charles Machan, Associate Professor, College and Graduate School of Arts & Sciences, University of Virginia
Hilinski, whose research group focuses on organic chemistry, emphasized the importance of the interdisciplinary nature of the research team.
This molecule that we use as a catalyst has a history in my laboratory, but we have always researched its use in chemical reactions that are performed on much larger, carbon-containing molecules – like the active ingredients in medicines. Without Charlie Machan’s expertise, I don’t think we would have made the connection to fuel cell chemistry.
Michael Hilinski, Associate Professor, College and Graduate School of Arts & Sciences, University of Virginia
The discovery may also affect the industrial production of hydrogen peroxide, a standard household product used in wastewater treatment and paper manufacturing.
Machan said, “The process of making hydrogen peroxide is environmentally unfriendly and very energy intensive. It requires high-temperature steam reforming of methane to release the hydrogen used to generate it.”
The Machan team's discovery may also enhance the catalytic part of that procedure, which could benefit businesses, the environment, and water treatment technology.
Hilinski further noted that the implications of this discovery and the teamwork that produced it may go far beyond energy storage.
Hilinski said, “Big picture, one of the most exciting things about this study is that by electrifying the catalyst, we have changed the way it reacts. This is something unexpected that could also be useful for the synthesis of medicines, which my research group is eager to explore.”
Machan, whose research group specializes in molecular electrochemistry, attributes the discovery to the interdisciplinary composition of the research team.
Machan concluded, “Without Mike Hilinski’s group’s know-how in making stable organic molecules that can undergo the kind of reactions necessary, the work wouldn't have been possible. This unique organic molecule enabled us to do something that normally only transition metals can do.”
Journal Reference:
Cook, N. E., et al. (2024) Metal-Free Homogeneous O_2 Reduction by an Iminium-Based Electrocatalyst. American Chemical Society. doi.org/10.1021/jacs.3c14549