Chemists propose spinach as a better, cheaper battery catalyst

While it's always been a boon to Popeye's "muskles," it looks like spinach may also have a role to play in clean future batteries.

spinach
Credit: Ataly/Shutterstock
  • Scientists are seeking sustainable, clean chemicals for use in future fuel cell and metal-air batteries.
  • Platinum is the current go-to substance for battery cathode catalysts, but it poses a number of problems, including high cost and instability.
  • Chemists at American University have developed a new high-performance catalyst from simple spinach, although its preparation as a catalyst is anything but simple.


    As we look to power tomorrow's devices sustainably and economically, there's a great deal of research going into the development of better, cleaner battery technology. Showing particular promise are fuel-cell and metal-air battery technologies. Though both continue to operate using the anode/cathode/electrolyte paradigm of current batteries, the race is on to find more sustainable materials that can replace those in current use. A new study published in the American Chemical Society's open-source journal ACS Omega proposes that one solution may be Popeye's favorite superfood: spinach.

    Cathodes and anodes, oh my

    Flow of energy when battery is in use, discharging

    Credit: VectorMine/Shutterstock/Big Think

    Electrons travel within a battery from one electrode, called the anode, through the battery's electrolyte — either a powder or liquid barrier — to another electrode, called the cathode. The anode releases these electrons through a chemical process called oxidation, while the cathode accepts them through another, an oxygen reduction reaction. Together, this exchange is called a "redox."

    The electrons' return trip back to the anode, however, requires a "load" provided by an external device, which is fine, since that device — a flashlight, a phone, or a car, for example — operates on the energy produced by the battery's electrons passing through.

    The electrons travel out from the cathode's positive terminal to the device then return to the battery's negative anode terminal. In this way the energy travels round and round the battery-device circuit. (When charging a battery, electrons go in the opposite direction connected to a charger.)

    The new study is concerned with the catalyst that produces the cathode's oxygen reduction reaction.

    Replacing a problematic, pricey catalyst

    platinum bricks

    Credit: AlexLMX/Shutterstock

    Fuel cell batteries and metal-air batteries use the surrounding air outside the battery as their cathode. It's clean, free, plentiful, and it works, as long as there's a catalyst that can adequately prompt the requisite oxygen reduction reaction.

    The most commonly used catalysts for such batteries have been based on platinum. There are problems with these, though. Of course, platinum is expensive. Also, as the study notes, "the lack of long-term stability and the vulnerability to surface poisoning by various chemicals such as methanol and carbon monoxide, call for the development of non-Pt group metal (NPGM) catalysts."

    Researchers have therefore been exploring non-toxic, carbon-based catalyst alternatives since they may be more stable and exhibit resistance to surface poisoning. And because carbon is everywhere, they'd be inexpensive to produce. However, some of the materials being investigated don't do the job as well as platinum-based catalysts. The chemical reaction they produce is slow, posing a speed bottleneck to the flow of electrons.

    Enter spinach

    Credit: Liu, et al./ACS Omega 2020, 5, 38, 24367-24378

    Shouzhong Zou, of American University's Department of Chemistry, is the paper's senior author. The lead author is Xiaojun Liu, with Wenyue Li as co-author. Professor Zou reports:

    "The method we tested can produce highly active, carbon-based catalysts from spinach, which is a 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."

    While other catalyst research has involved plants such as rice and cattails, Zou believes spinach has a few things that make it a superior candidate as a catalyst material. For one thing, it's rich in iron and nitrogen, both essential catalyst ingredients. In addition, it's easy and inexpensive to grow, and it's abundant.

    Zou and his students developed spinach-based carbon nanosheets a thousand times thinner than a human hair. The process is complex, a combination of basic and advanced techniques.

    To begin, the researchers washed, juiced, and freeze-dried the vegetable before grinding it by hand into a fine powder using a mortar and pestle. Next, the spinach powder was dissolved and mixed with melamine, sodium chloride, and potassium chloride in water and cooked together at 120°C. This mixture was then rapid-cooled in liquid nitrogen and freeze-dried. Then it was pyrolized twice.

    It may well have been worth the effort. Measurements of the resulting nanosheet indicated that it can out-perform platinum as a catalyst in both speed and stability. Of course, that's on top of being made from such an unassuming, inexpensive, and widely available plant.

    "This work," says Zou, "suggests that sustainable catalysts can be made for an oxygen reduction reaction from natural resources." The next step for Zou and his students is to try out their spinach catalyst in prototype fuel cells to assess its performance in action. They're also looking into the use of other plant materials for catalysts.

    Finally, Zou understandably hopes to develop a simple, less energy-intensive way to make their catalyst nanosheets.

    This is what aliens would 'hear' if they flew by Earth

    A Mercury-bound spacecraft's noisy flyby of our home planet.

    Image source: sdecoret on Shutterstock/ESA/Big Think
    Surprising Science
    • There is no sound in space, but if there was, this is what it might sound like passing by Earth.
    • A spacecraft bound for Mercury recorded data while swinging around our planet, and that data was converted into sound.
    • Yes, in space no one can hear you scream, but this is still some chill stuff.

    First off, let's be clear what we mean by "hear" here. (Here, here!)

    Sound, as we know it, requires air. What our ears capture is actually oscillating waves of fluctuating air pressure. Cilia, fibers in our ears, respond to these fluctuations by firing off corresponding clusters of tones at different pitches to our brains. This is what we perceive as sound.

    All of which is to say, sound requires air, and space is notoriously void of that. So, in terms of human-perceivable sound, it's silent out there. Nonetheless, there can be cyclical events in space — such as oscillating values in streams of captured data — that can be mapped to pitches, and thus made audible.

    BepiColombo

    Image source: European Space Agency

    The European Space Agency's BepiColombo spacecraft took off from Kourou, French Guyana on October 20, 2019, on its way to Mercury. To reduce its speed for the proper trajectory to Mercury, BepiColombo executed a "gravity-assist flyby," slinging itself around the Earth before leaving home. Over the course of its 34-minute flyby, its two data recorders captured five data sets that Italy's National Institute for Astrophysics (INAF) enhanced and converted into sound waves.

    Into and out of Earth's shadow

    In April, BepiColombo began its closest approach to Earth, ranging from 256,393 kilometers (159,315 miles) to 129,488 kilometers (80,460 miles) away. The audio above starts as BepiColombo begins to sneak into the Earth's shadow facing away from the sun.

    The data was captured by BepiColombo's Italian Spring Accelerometer (ISA) instrument. Says Carmelo Magnafico of the ISA team, "When the spacecraft enters the shadow and the force of the Sun disappears, we can hear a slight vibration. The solar panels, previously flexed by the Sun, then find a new balance. Upon exiting the shadow, we can hear the effect again."

    In addition to making for some cool sounds, the phenomenon allowed the ISA team to confirm just how sensitive their instrument is. "This is an extraordinary situation," says Carmelo. "Since we started the cruise, we have only been in direct sunshine, so we did not have the possibility to check effectively whether our instrument is measuring the variations of the force of the sunlight."

    When the craft arrives at Mercury, the ISA will be tasked with studying the planets gravity.

    Magentosphere melody

    The second clip is derived from data captured by BepiColombo's MPO-MAG magnetometer, AKA MERMAG, as the craft traveled through Earth's magnetosphere, the area surrounding the planet that's determined by the its magnetic field.

    BepiColombo eventually entered the hellish mangentosheath, the region battered by cosmic plasma from the sun before the craft passed into the relatively peaceful magentopause that marks the transition between the magnetosphere and Earth's own magnetic field.

    MERMAG will map Mercury's magnetosphere, as well as the magnetic state of the planet's interior. As a secondary objective, it will assess the interaction of the solar wind, Mercury's magnetic field, and the planet, analyzing the dynamics of the magnetosphere and its interaction with Mercury.

    Recording session over, BepiColombo is now slipping through space silently with its arrival at Mercury planned for 2025.

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    • Instead of the 'Rank and Yank' method once used by GE, Meyer explains how Netflix managers use the 'keeper test' to determine if employees are crucial pieces of the larger team and are worth fighting to keep.
    • "An individual performance problem is a systemic problem that impacts the entire team," she says. This is a valuable lesson that could determine whether the team fails or whether an organization advances to the next level.
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