Syzygy Plasmonics

It comes down to photocatalytics; this team has been working for more than 30 years to develop its "antenna-reactor" plasmonic photocatalysts. These are nanoparticles of a catalyst, dotted with little clumps of an "antenna" material designed to increase the catalyst's ability to absorb light. Properly tuned, these antenna-reactor particles take in energy from ambient light – be it sunlight, or light from low-energy LEDs – and kick out short-lived "hot electrons" with enough energy to start an efficient chemical reaction even at ambient temperatures. 

Antenna-reactor photocatalysts can be designed for all sorts of reactions. This is the same team, and essentially the same underlying idea, behind the light-powered hydrogen sulfide-to-hydrogen catalyst we wrote about a few weeks ago, for example. That one used silicon dioxide as the "reactor" catalyst, with tiny particles of gold as the "antenna" drawing energy in from light. 

This ammonia-splitting photocatalyst uses iron as its reactor, and copper as its light-collecting antenna – both cheap and abundant metals, as opposed to the typical copper-ruthenium thermal catalysts used today. In lab testing, according to Rice alumnus and study co-author Hossein Robatjazi, "under illumination, the copper-iron showed efficiencies and reactivities that were similar to and comparable with those of copper-ruthenium."

The small laser-powered cell used in initial lab tests (left) vs the much larger, laser-powered test rig at Syzygy

Syzygy Plasmonics

The initial tests were conducted using light supplied by lasers, in a tiny experimental setup. But study co-author Naomi Halas is also a co-founder of Syzygy Plasmonics, a well-funded company set up to commercialize the Rice team's work, and Syzygy was able to license this particular catalyst and build a test rig some 500 times larger, using efficient LED lighting instead of lasers. The catalyst remained just as efficient. 

“This is the first report in the scientific literature to show that photocatalysis with LEDs can produce gram-scale quantities of hydrogen gas from ammonia,” Halas said. “This opens the door to entirely replace precious metals in plasmonic photocatalysis.”

So, going back to why we should care about all this, the copper-iron photocatalyst should make it much cheaper and easier to extract hydrogen from ammonia. But it'll also do it without needing heat, so there'll be energy and emissions saved as well. 

Perhaps most importantly, this looks like it'll lead to an ammonia cracking device that's small, reliable, lightweight, and cool rather than running at hundreds of degrees. Something that doesn't need a full-scale facility to operate. Syzygy says its initial Rigel Photocatlytic Reactor product is about the size of a small washing machine, and processes around a ton a day, depending on the specific reaction it's running. These can be stacked; you can run a bunch of them simultaneously if you need a greater output.

Syzygy's Rigel photocatlytic reactor is about the size of a washing machine (right) but it can be deployed in banks (left)

Syzygy Plasmonics

Perhaps you could stick a bank of these on an electric cargo ship, converting easily-stored ammonia into easily-used hydrogen right where it's needed. That in itself could be absolutely revolutionary, radically boosting the range of clean cargo and passenger shipping. 

Perhaps the concept might prove small and light enough to be relevant in aviation, where the energy density of hydrogen stored in ammonia could open up range figures that are currently out of reach without jet fuel. Perhaps it might eventually be small enough to stick in an electric car you can fill up with ammonia at a gas station. 

And that's just this particular photocatalyst; the Rice and Syzygy teams are certainly not stopping here. Indeed, the company's target is to put thermal catalysts out of a job wherever they can. 

“Given their potential for significantly reducing chemical sector carbon emissions, plasmonic antenna-reactor photocatalysts are worthy of further study,” added another co-author, Emily Carter. “These results are a great motivator. They suggest it is likely that other combinations of abundant metals could be used as cost-effective catalysts for a wide range of chemical reactions.”

An earlier palladium/aluminum catalyst shown in detail. Colored electron spectroscopy maps show the "spatial distribution of individual plasmon modes around the palladium islands. These plasmon modes are responsible for capturing light energy and transferring it to the catalyst particles."

Rice University

"Catalysis is the foundation of chemical industry," says yet another co-author and Syzygy co-founder Peter Nordlander, "and it's one of the most energy-consuming parts of all society." 

"We show in this work," adds Halas, "that LED-based chemistry is actually doable, and it's doable at scale. It can contribute to industrial-scale chemistry, and industrially-important reactions."

Syzygy says it's already got this reaction up and running in field trials, and that it expects to have these photocatalytic ammonia-cracking reactors commercially available in 2023.

This is some very exciting technology, with huge potential across a range of industries and as a contributor to decarbonization. Learn more in the video below.

 

 

Loz has been one of our most versatile contributors since 2007. Joining the team as a motorcycle specialist, he has since covered everything from medical and military technology to aeronautics, music gear and historical artefacts. Since 2010 he's branched out into photography, video and audio production, and he remains the only New Atlas contributor willing to put his name to a sex toy review. A singer by night, he's often on the road with his acappella band Suade.

 

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