A cleaner route to ammonia


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Apr 14, 2023

A cleaner route to ammonia

James Mitchell Crow is a freelance writer, based in Melbourne, Australia. You

James Mitchell Crow is a freelance writer, based in Melbourne, Australia.

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Douglas Macfarlane, chief scientific officer at Jupiter Ionics, hopes to produce green fertilizer.Credit: Steve Morton/Jupiter Ionics

Jupiter Ionics in Melbourne, Australia, spun off from Monash University, Melbourne, in 2021.

It is a curious quirk of chemistry that when lithium atoms work together, they can break one of the strongest known chemical bonds. Lithium can take the triple-bonded nitrogen molecule (N2) and, under ambient conditions, break it in two.

Jupiter Ionics in Melbourne, Australia — a finalist in The Spinoff Prize 2023 — aims to harness this chemistry to make ammonia (NH3).

Ammonia is crucial to produce synthetic fertilizer, which the world relies on to grow crops. Since the early 1900s, ammonia has been made by the industrial Haber–Bosch process. Global ammonia production now reaches 150 million tonnes per year.

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"Haber–Bosch is a very central piece of chemistry in the world today, but it is reliant on fossil fuels," says Douglas Macfarlane, an electrochemistry researcher at Monash University in Melbourne, and Jupiter Ionics’ founder and chief scientific officer. The process operates at high pressure and temperature, and in large, centralized, continually operating plants that are difficult to marry with the comparatively small-scale, intermittent nature of renewable energy, Macfarlane explains. Haber–Bosch is responsible for an estimated 1.5% of global carbon emissions, and its contribution continues to grow.

Macfarlane's Monash laboratory has pioneered a high-selectivity, lithium-mediated electrochemical pathway to ammonia. The process uses air, water and renewable electricity. In 2021, Macfarlane founded Jupiter Ionics to scale up and commercialize the process. Producing green fertilizer is the initial goal, but generating ammonia as a carbon-free fuel is also a prospect. Jupiter's technology is closing in on the US Department of Energy's target of achieving carbon-free production of ammonia at a rate that is commercially competitive with Haber–Bosch.

The idea of pulling apart nitrogen molecules to make ammonia using an electrical current, rather than high temperatures and pressures, goes back a century1. The electrodes in an electrochemical cell can split N2 in a catalyst-mediated process, then combine the atoms with protons (H+) sourced from water to form ammonia.

That is the theory at least, says chief executive of Jupiter Ionics, Charles Day. "People have made tiny amounts of ammonia, but to be commercially relevant you need to be able to produce it at a significant rate," says Day, a chemical engineer turned technology commercialization executive. Day was initially engaged by Monash to write the company's business plan, before becoming the inaugural chief executive.

Part of Nature Outlook: The Spinoff Prize 2023

The challenge lies in suppressing a side reaction in which the cell takes the simpler path of combining pairs of protons to produce hydrogen gas (H2), instead of ammonia. Hydrogen is usually the predominant product in the electrochemical process. The problem, known as the selectivity challenge, is described by a metric called faradaic efficiency (FE): the amount of ammonia produced relative to the ammonia that could be generated based on electrical input. Until a few years ago, ammonia selectivity of only 5–20% FE had been reported.

In 2019, after assessing several candidate electrocatalyst systems and making little to no ammonia, Macfarlane's Monash team tried lithium. "It had become quite well known in the lithium battery world that lithium will react with nitrogen," Macfarlane recalls. "That's the tantalizing step, that you can bust open the nitrogen molecule with lithium."

The key chemistry of the lithium-mediated process happens at the cathode of the electrochemical cell. Here, lithium and nitrogen react to form lithium nitride (Li3N). This intermediate reacts with protons (generated at the anode) to release ammonia and regenerate the lithium (see ‘The electrochemical ammonia cell’).

Credit: Alisdair MacDonald

In 2021, Macfarlane and his colleagues reported2 that by adding a phosphorus-based proton shuttle to mediate proton delivery to the cathode, they had reached 69% FE. A year later, they reported3 that by switching to an electrolyte that better supported the lithium-mediated nitrogen-splitting step, they had hit almost 100% FE. "To be commercially relevant, the selectivity needs to be basically at 100%, which is what our most recent paper finally reported," Macfarlane says.

These levels of ammonia production are a significant step forward and place the team at the forefront of the field, says Karthish Manthiram, an electrochemist working on ammonia production at the California Institute of Technology in Pasadena, who is not affiliated with the company. "I thought it would take the community a few more years to achieve the results they have reported," Manthiram says. Jupiter Ionics's results, he adds, suggest that this is a good time to commercialize the research and pursue it in a "more nimble, results-oriented" environment.

Scaling up the technology, while demonstrating stability and longevity, will be key challenges, according to Manthiram. "It is a high-risk endeavour," he says. "It's a matter of when, not if, electrochemical ammonia production will work — but the timing is always the hard part to predict."

Jupiter Ionics launched in April 2021, raising Aus$2.5 million (US$1.7 million) in seed funding. In March 2022, the company won a further Aus$2.65 million from the Australian government to lead a consortium of companies to develop its green ammonia-manufacturing technology. Using this collective funding, the company has grown to a team of about a dozen people, says Day.

Readying the process for the real world means shifting from a small-batch operation to a scalable reactor that produces ammonia in a continuous stream. "Separately, the anode side and the cathode side of the flow process are now working well," says Irina Simonova, an electrochemistry researcher at the company. "We are now focusing on getting the two sides working well together," she says. Both electrodes must carry the same current — they are two parts of the same electrical circuit — but at the moment each electrode has its own optimum current per unit area (the current density). The team is working to tune each electrode's area and thickness to achieve the current-density sweet spot.

The company plans to return to the market later this year to raise ‘series A’ investment, Day says. "As we scale up, the reactors get bigger and more expensive. The next round of investment is to start scaling up to something more like a product we could sell."

Jupiter Ionics has strong technology that targets a real need, and it also has a solid team and business plan, says Bob Gatte, a judge for The Spinoff Prize 2023 and chief executive of HighT-Tech in College Park, Maryland, which won the prize in 2021. "If their first pathway to commercialization doesn't work, they have other options."

The team has identified several potential routes to revenue generation. "We have the option to make entire systems ourselves, or to license our technology to other companies," Day says. "We’re still evaluating which of those makes most sense for us."

Also on the horizon is an emerging market for green ammonia in the energy sector. Increasingly, ammonia generated from renewable sources is recognized as a potential energy carrier — a way to convert renewable energy into a chemical form that can be readily stored, transported or even shipped.

"We’re initially focusing on fertilizer because it is addressing today's problem, today," says Day. "There is a near-200-million tonne per annum ammonia market which needs to decarbonize as fast as possible. But we certainly want to play a part in developing ammonia as an energy carrier," he says.

"Energy offers potential upsides on top of their main focus," Gatte says. "Now, they have to prove the technology is scalable."

doi: https://doi.org/10.1038/d41586-023-01659-w

This article is part of Nature Outlook: The Spinoff Prize 2023, an editorially independent supplement produced with the financial support of third parties. About this content.

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