Energy experts looking to find a replacement for fossil fuels in heavy industry and transportation have long thought that hydrogen could be the ideal replacement fuel.
It can be made using renewable energy and water, and, when passed through an electrolyzer, the only emission is water making the fuel mainly pollution free.
However, hurdles such as the cost to store and retrieve hydrogen blocks the green, high energy density, and zero-carbon fuel from reaching scale. A discovery from researchers at Rice and Princeton universities may have found an answer.
50 years after John Bockris first described the hydrogen economy in Science, the journal published a study describing what may be a key factor in realizing his utopia. In the recent report, researchers from Rice and Stanford demonstrated a low-cost technique that combines iron, copper, and a simple LED light to locally create, store, and retrieve this green fuel.
It was John Bockris who first used the term 'Hydrogen economy' in 1972. In that groundbreaking paper for Science, Bockris wrote: “The medium of energy transport from an atomic reactor to sites at which energy is required should not be electricity, but hydrogen.” He went on, writing, “The term ‘hydrogen economy’ applies to energetic, ecological, and economic aspects of this concept.”
In the summer 1972 publication of the journal Science, Bockris imagined a future of “atomic reactors held on platforms floating on water,” whose electricity would be converted “on site to hydrogen and oxygen by electrolysis,” the action of using electricity to split the H2 and O in water.
When Bockris looked into the future, he saw hydrogen-powered cars, just as efficient as then-gas powered cars, taking to the streets. He saw airplanes and jets running on liquid hydrogen with an even longer range, taking to the skies. He saw cheaper production of aluminum, iron, and ammonia by way of hydrogen. And he saw fusion reactors powered by hydrogen’s byproduct deuterium, all while providing more drinking water for a growing population.
“We hear a lot about hydrogen being the ultimate clean fuel, if only it was less expensive and easy to store and retrieve for use,” Naomi Halas, a professor at Rice University and one of the study’s principal authors, said in a statement.
“This result demonstrates that we are moving rapidly towards that goal, with a new, streamlined way to release hydrogen on-demand from a practical hydrogen storage medium using earth-abundant materials and the technological breakthrough of solid-state lighting.”
Nowadays, almost all hydrogen produced is catalyzed by natural gas through a well-established, large-scale, and low-cost, but polluting fossil fuel-based process.
Electrolysis which splits hydrogen from oxygen in water remains equally well-established and viable, but as researchers from Rice and Princeton universities describe in their recent paper, the high energy losses of electrolysis holds it back.
In recent years scientists are employing different chemicals to transport and store hydrogen, in attempts to make the process less costly.
According to the researchers, one of the most promising chemicals is ammonia. Atomically, ammonia is written as NH3, with a structure of three hydrogen atoms and one nitrogen atom. Ideally, ammonia’s existing avenues for safe transportation and storage could be leveraged for its main component, hydrogen.
A recent American Chemical Society review of present ammonia/hydrogen research revealed that ammonia’s low-pressure liquefaction enables it to be transported and stored at lower amounts of energy than hydrogen.
Currently, ammonia’s decomposition reaction is used for industrial purposes, but if used for clean hydrogen, the review says it has the potential to drive the hydrogen economy.
“This discovery paves the way for sustainable, low-cost hydrogen that could be produced locally rather than in massive centralized plants,” Peter Nordlander, a professor at Rice and another principal author, said in a statement.
Nordlander and Halas are the co-founding scientists of Syzygy Plasmonics, a startup aiming to electrify chemical manufacturing, making it cleaner using the power of light.
With their LED-powered reactors, Syzygy aspires to achieve one gigaton of carbon emissions reductions by 2040, a mission helped along by the startup’s recent $76 million Series C funding round. With the duo’s recent research study with Princeton researcher, Emily Carter, they may be onto another breakthrough.
Presently, ammonia’s industrial applications ‘crack’ the compound at high temperatures, using materials that accelerate the chemical reaction without being charged by the reaction. However, these materials, such as the metal ruthenium, are, you guessed it, expensive. The process itself also has a relatively high energy cost.
The researchers wanted to find ways to use nanotechnology to allow cheaper elements like copper and iron to act as a catalyst, while tackling the energy cost as a whole. For the latter, the researchers turned to light. Present ammonia decomposition heats the compound to astronomically high temperatures, using the heat to break the molecules. With light, the researchers hypothesized they could sever the chemical bonds, slicing them apart with surgical precision, rather than using the heat to make them explode.
Combining light with tiny metals is known as plasmonics, an emerging field and the basis of Halas and Nordlander’s startup Syzygy. The light-slicing comes from their past research.
Together, the research team consistently extracted hydrogen from ammonia using only light from energy-efficient LEDs. According to the researchers, while the process is scalable, further research will investigate other possible catalysts, as to not solely rely on iron and copper. Hopefully, the researchers say, investigation could lead to an even lower cost and higher efficiency.
“Hydrogen is used ubiquitously in industry and will be used increasingly as fuel as the world seeks to decarbonize its energy sources,” Carter said in a statement.
“However, today it is mostly made unsustainably from natural gas – creating carbon dioxide emissions – and is difficult to transport and store. Hydrogen needs to be made and transported sustainably where it is needed. If carbon-emission-free ammonia could be produced, for example, by electrolytic reduction of nitrogen using decarbonized electricity, it could be transported, stored, and possibly serve as an on-demand source of green hydrogen using the LED-illuminated iron-copper photocatalysts reported here.”
With the power of light, iron, copper, and ammonia, the world could be one step closer to realizing the carbon-free hydrogen economy, or at least, enabling the fuel to play a viable role in the energy transition.