Amazing Carbon Nanosheets from Spinach May Energize Fuel Cells

Popeye knew something that no one else did

When we were kids, our moms demanded that we eat our yucky spinach. And they would point to Popeye as a sterling example of why – at least for some of us. Perhaps Popeye knew the real secret of spinach.

Researchers are now learning that this hearty, green vegetable doesn’t only provide energy to people. It has also demonstrated an ability to power fuel cells, as indicated in a newly published paper (ACS Omega, “Spinach-Derived Porous Carbon Nanosheets as High-Performance Catalysts for Oxygen Reduction Reaction“) written by scientists from AU’s Department of Chemistry.

Transforming Spinach

It seems that it becomes a significant catalyst for oxygen reduction reactions within metal-air batteries and fuel cells whenever spinach is transformed into carbon nanosheets.

One of the two reactions required by fuel cells and metal-air batteries is the oxygen reduction reaction. Also, the oxygen reduction reaction is the slower of the two reactions and limits the device’s energy output.

Scientists had suspected for a long time that certain carbon materials could catalyze this reaction. But the problem has always been that other carbon catalysts never perform any better than the platinum-based catalysts that have been traditionally used.

Seeking a Cheaper More Effective Carbon Catalyst

The AU scientists desired to discover a different carbon catalyst that was less expensive, less toxic, and more effective. It seemed logical to consider natural resources as a potential candidate. They decided to give spinach a try.

“This work suggests that sustainable catalysts can be made for an oxygen reduction reaction from natural resources,” stated Prof. Shouzhong Zou, who is a chemistry professor at AU and the research paper’s lead author.

“The method we tested can produce highly active, carbon-based catalysts from spinach, which is renewable biomass. In fact, we believe it outperforms commercial platinum catalysts in both activity and stability. The catalysts are potentially applicable in hydrogen fuel cells and metal-air batteries.”

Zou’s former doctoral pupils Wenyue Li and Xiaojun Liu and undergraduate student Casey Culhane were co-authors of the research paper.

The purpose of carbon catalysts

Catalysts are necessary to accelerate an oxygen reduction reaction so that sufficient current is generated to create energy. The practical applications driving the need for fuel cells and metal-air batteries are electric vehicles’ powering and different kinds of military equipment. Researchers have been making remarkable progress in the lab and prototypes where plant-derived catalysts have been used, such as rice and cattail grass.

Zou’s work is the first where spinach was used to prepare oxygen reduction reaction-catalysts. Researchers believe that spinach is a perfect candidate for this work as it can survive in low temperatures. It is very abundant and simple to grow. It contains lots of nitrogen and iron, which are vital for this kind of catalyst.

Zou and his team created and tested these spinach-derived carbon nanosheets. Carbon nanosheets are much like a sheet of paper as it has a nanometer-scale thickness, which is roughly one thousand times thinner than a human hair.

These nanosheets’ creation begins with researchers putting spinach through a rigorous multi-step process that includes both high- and low-tech methods such as washing, juicing, and freeze-drying. The spinach is then manually ground into a fine powder using a mortar and pestle. Then extra nitrogen is added to the mixture to enhance its performance.

Data from these spinach-derived catalysts have shown a marked improvement over the traditionally used platinum-based catalysts. This is encouraging news because platinum catalysts are much more expensive and tend to lose potency over time.

What’s left for the researchers is to move these spinach-based catalysts from the lab and into prototype devices, like hydrogen fuel cells, to evaluate their performance in these environments. Scientists intend to also address sustainability by lowering the energy needed for the overall process.

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