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Better catalysts from super-fast heating

Close-up image of a see through window into a high-temperature furnace where a small alloy is alight

HighT-Tech’s furnace heats the company’s material extremely quickly, allowing the creation of new metal alloys.Credit: High-T Tech

HighT-Tech is a spin-off of the University of Maryland, College Park, and winner of The Spinoff Prize 2021.

Chemical synthesis can be a costly proposition. Take, for instance, the production of nitric acid, used to make fertilizer. One step in the process involves heating ammonia and passing it through a gauze made of platinum and rhodium, which act as catalysts to make the reaction more efficient. But those metals are expensive. Over the past year, the price of platinum has climbed from about US$25 per gram to more than $40 per gram, whereas rhodium has soared from roughly $275 per gram to more than $900 per gram.

HighT-Tech in College Park, Maryland, is developing a method to make catalysts with the same performance as conventional ones from combinations of cheaper metals, or better. The process, it says, could allow the company to fine-tune the catalytic activity of the materials and discover new and potentially more efficient catalysts. “What we’re trying to do is create a product that has a much lower platinum content that would give you the same performance,” says chemical engineer Bob Gatte, who previously worked at the chemical company W. R. Grace in Columbia, Maryland, and joined HighT-Tech as chief executive in February. “Millions of dollars’ worth of catalysts go into these reactors.”

The company’s process is based on research1 by Liangbing Hu, a materials scientist at the University of Maryland in College Park and co-founder of the company. It involves heating the materials so rapidly that different metals can mix, even when this wouldn’t be possible with conventional melting processes. Conventional metal alloys usually involve just two elements, with the proportion of one far outweighing that of the other. One method for making catalysts developed over the past few years, for example, is to create nanoparticles of a primary metal, such as nickel, coated by a thin shell of another metal, such as gold.

But high-entropy alloys, such as those being developed by HighT-Tech, can mix several elements together, and often distribute them in equal ratios. That changes how the atoms interact with each other, and therefore alters the way the alloy behaves. “We can finely tune the properties, like catalytic properties, by adjusting the different elements’ ratios,” says Chengwei Wang, a researcher in Hu’s lab and vice-president of HighT-Tech. “Because we can add multiple elements, we can have a similar performance to a precious-metal catalyst by using this cheap metal.”

To build their material, the scientists start with carbon nanofibres. Various metals are dissolved with chloride to form metal salts; these are then mixed together and the mixture is coated onto the nanofibres. The researchers send a jolt of current through the conductive fibres. Because everything is so thin, and the metal is in direct contact with the carbon, the entire mixture heats up rapidly — to about 2,000 kelvin in 55 milliseconds. This method, called carbothermal shock, mixes the metals in the coating together. When the current is turned off, the thinness of the material means it cools as rapidly as it heats up — a process that does not give the metals time to separate (see ‘Thermal-shock synthesis’). “You basically freeze the atoms in place in this high-entropy state,” Gatte says. Locking them in that state changes their electronic properties, giving them higher catalytic activity, better selectivity for a particular substance and more stability, he says.

Thermal-shock synthesis

Credit: SEM images reprinted with permission from Yao, Y. et al. Science 359, 1489–1494 (2018).

In addition to improving catalytic properties and reducing the quantities of precious metals required, the process might also lower costs by more efficiently using the energy that goes into heating the materials, Gatte says.

Early promise

High-entropy alloys are attracting a lot of attention for various applications, including as catalysts. The company’s technology shows promise, says Justin Notestein, a chemical engineer at Northwestern University in Evanston, Illinois, who is not affiliated with the company. But a lot of work is needed to make such materials practical, including dealing with the possible effects of the carbon on the catalysis process. The method also seems to produce small quantities of material. “Scale-up seems like it could be tricky. Large chemical reactors in industry might be filled with several tonnes of catalyst,” Notestein says. Wang says the company currently produces catalysts at a rate of 10 grams per hour, but it is developing a manufacturing process that should make it easy to reach rates of 1 kilogram per hour or even higher, which might make meeting industry requirements possible.

The thermal-shock approach is a versatile but simple method that could have a big impact on manufacturing, says Lewis Liu, a venture capitalist and judge for The Spinoff Prize. Liu is impressed that the company chose a niche product to start with and developed “a clear and focused commercial strategy”.

The company’s current focus is developing catalysts for ammonia synthesis. This is a big market, and the chemistry is relatively straightforward, so it easy to evaluate how well the catalysts are working, Gatte says. Further down the road, however, its technology might make materials for catalytic converters in cars, emission systems in power plants and a variety of chemical reactions that rely on expensive noble-metal catalysts, such as refining petroleum.

So far, the company has used mixtures of between three and ten elements, mixing transition metals with noble metals or rare-earth elements. “The process is theoretically applicable to any of the metals in the periodic table,” Gatte says. To begin with, the company’s focus is on trying to replace most of the platinum used in the synthesis of ammonia. It could take another two to three years to have a demonstration project, he says, and the company is in early talks with chemical firms about providing manufacturing capability to do that. Gatte says the company is evaluating different business models, including manufacturing the catalysts themselves, signing a joint development agreement with an industrial partner or licensing their technology to other manufacturers.

HighT-Tech is supported by the Maryland Energy Innovation Accelerator, a state-funded project in College Park that helps clean-energy start-ups get off the ground. Hu is also working on a separate start-up at the accelerator using the thermal-shock process to build better membranes for batteries. HighT-Tech’s main funding has come from three grants, totalling about US$700,000, from the US Advanced Research Project Agency—Energy (ARPA-E). Wang says the group is applying for further ARPA-E grants and other government funding and beginning to talk to venture capitalists about financing.

HighT-Tech is still a very small company — other than Wang and Gatte, the only other employee is chemist Yuhui Gong, the chief technology officer. The company licenses two main patents from the University of Maryland that cover the process of creating the high-entropy alloys. Further patents could be filed for individual alloys, Wang says.

Although the initial focus is on making catalysts, Gatte says that the company is considering what other products the thermal-shock technology could deliver. “It’s also applicable to battery materials, membranes and especially inorganic materials,” he says. “Catalysts is the primary one right now, but we think there’s potential in other areas as well.”

If that turns out to be true, thermal-shock technology might jolt manufacturers into new ways of making their products.

doi: https://doi.org/10.1038/d41586-021-01665-w

This article is part of Nature Outlook: The Spinoff Prize 2021, an editorially independent supplement produced with the financial support of third parties. About this content.

Updates & Corrections

  • Update 13 July 2021: This article has been updated to reflect the fact that HighT-Tech won The Spinoff Prize.

References

  1. 1.

    Yao, Y. et al. Science 359, 1489–1494 (2018).

    PubMed  Article  Google Scholar 

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