Researchers have found a faster and more efficient method of producing CoSn(OH)6, a potent catalyst for high-energy lithium-air batteries.
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CoSn(OH)6 (CSO) is a powerful oxygen evolution reaction (OER) catalyst that is required for the development of next-generation lithium-air batteries. However, current CSO synthesis methods are difficult and time-consuming.
Recently, an international research team used solution plasma to create CSO nanocrystals with good OER catalytic capabilities in a single process in 20 minutes. Their observations could aid in the production of high energy density batteries.
With global warming on the rise, it is vital to lessen reliance on fossil fuels and transition to alternative green energy sources. The advancement of electric vehicles is a step in this direction. Electric vehicles, on the other hand, require high energy density batteries to function, and ordinary lithium-ion batteries are inadequate.
Lithium-air batteries, in theory, have a higher energy density than lithium-ion batteries. However, before they can be used in practice, these batteries must be made more energy efficient, their cycle characteristics improved, and the overpotential required to charge/discharge the oxygen redox process lowered.
To tackle these challenges, a suitable catalyst to expedite the oxygen evolution reaction (OER) inside the battery is required. The OER is a significant chemical reaction in water splitting that improves the performance of storage batteries. Rare and costly noble metal oxides like ruthenium(IV) oxide (RuO2) and iridium(IV) oxide (IrO2) have traditionally been utilized as catalysts to accelerate the OER of metal-air batteries.
Transition metals, like perovskite-type oxides and hydroxides, are known to be very active for the OER and are hence cheap catalytic materials. CoSn(OH)6 (CSO) is a perovskite-type hydroxide that has been identified as a promising OER catalyst. However, existing CSO synthesis methods are time-consuming (over 12 hours) and involve many stages.
In a recent advance, a research team directed by Prof. Takahiro Ishizaki from Shibaura Institute of Technology in Japan, along with Masaki Narahara and Dr. Sangwoo Chae, synthesized CSO in just 20 minutes using only a single step.
The team employed a solution plasma process, a cutting-edge approach for material synthesis in a nonthermal reaction field, to accomplish this astonishing achievement. On April 17th, 2023, their findings were published in Issue 11 of the journal Sustainable Energy & Fuels.
Using X-Ray diffractometry, the researchers demonstrated that highly crystalline CSO could be produced from a precursor solution by increasing the pH to values larger than 10 to 12. Using a transmission electron microscope, they discovered that the CSO crystals were cube-shaped and ranged in size from 100 to 300 nm.
The researchers also employed X-Ray photoelectron spectroscopy to examine the composition and binding sites of CSO crystals, discovering divalent Cobalt (Co) and tetravalent Tin (Sn) within the complex. Finally, the researchers used an electrochemical approach to investigate the capabilities of CSO as an OER catalyst. They discovered that synthesized CSO had a 350 mV overpotential at a current density of 10 mA cm−2.
CSO synthesized at pH12 had the best catalytic property among all samples synthesized. In fact, this sample had slightly better catalytic properties than that of even commercial-grade RuO2.
Takahiro Ishizaki, Professor, Shibaura Institute of Technology
This was validated when the pH 12 sample was revealed to have the lowest potential, 104 mV lower than the commercially available RuO2 vs. reversible hydrogen electrode at 10 mA cm−2.
All in all, this study provides a simple and effective method for synthesizing CSO for the first time. This technique makes CSO viable for use in lithium-air batteries, paving the way for the development of next-generation electric batteries.
The synthesized CSO showed superior electrocatalytic properties for OER. We hope that the perovskite-type CSO materials will be applied to energy devices and will contribute to the high functionalization of electric vehicles. This, in turn, will bring us one step closer towards achieving carbon neutrality by enabling a new energy system independent of fossil fuels.
Takahiro Ishizaki, Professor, Shibaura Institute of Technology
Journal Reference:
Narahara, M., et al. (2023). Solution plasma synthesis of perovskite hydroxide CoSn(OH)6 nanocube electrocatalysts toward the oxygen evolution reaction. Sustainable Energy & Fuels. doi.org/10.1039/D3SE00221G.