Baking soda solution for clean hydrogen storage
(Nanowerk News) In a world with steadily warming temperatures, a growing consensus demands that energy sources have zero, or near zero, carbon emissions. That means growing beyond coal, oil and natural gas by getting more energy from renewable sources.
One of the most promising carriers of renewable energy is clean hydrogen, which is produced without fossil fuels.
It’s a promising idea because the most abundant element in the universe is hydrogen, which is found in 75 percent of all matter. In addition, the hydrogen molecule has two paired atoms—the non-toxic and highly flammable Gemini twins.
The potential for burning hydrogen makes it a subject of great interest to energy researchers around the world.
At the Pacific Northwest National Laboratory (PNNL), a team is investigating hydrogen as a medium for storing and releasing energy, mostly by breaking its chemical bonds. Much of their work is associated with the Advanced Hydrogen Materials Research (HyMARC) consortium at the Department of Energy (DOE).
Hydrogen storage is not optimal
One focus of PNNL’s research has to do with optimizing hydrogen storage, a stubborn problem. Until recently, there was no completely safe, cost-effective, and energy-efficient way to store hydrogen on a large scale.
Hydrogen-based storage efforts at PNNL are funded by DOE’s Hydrogen and Fuel Cell Technology Office in the Office of Energy Efficiency and Renewable Energy (EERE). Research advances DOE (email protected) initiative as well as the institution Hydrogen shot.
new paper (Green Chemistry, “Using Earth’s abundant materials for long-term energy storage: the electro-chemical and thermo-chemical cycles of bicarbonate/formate”) the two lead authors are chemist and PNNL Laboratory Fellow Thomas Autrey and colleague Oliver Gutiérrez, an expert in making chemical reactions fast and cost-effective.
“You have to get a little creative,” says Autrey, who takes comfort in common, inexpensive, mild baking soda as a potential answer to big problems (Journal of Energy Storage, “Define long duration energy storage”). “Not all chemicals will be efficient at storing hydrogen. You have to work with what Mother Nature gives you.
Clean hydrogen for long-term energy needs
Autrey, Gutiérrez and others at PNNL see long-term energy storage as key to hydrogen’s future as a renewable energy carrier.
Current battery technology is designed for multiple hours of storage. In a renewable energy grid, batteries can handle about 80 percent of storage needs.
But “the final 20 percent will take a unique approach,” says Autrey. “We want to store excess energy to prepare dark languor.”
It is a German word that describes conditions without sufficient solar and wind energy potential. During Dunkelflaute’s dark, windless periods, the network needed a way to store energy for more than a few hours.
Seasonal storage capability like this is one of hydrogen’s attractions. So is the fact that hydrogen storage can occur anywhere―which is “geographically agnostic”, as experts say. A hydroelectric plant, for example, requires a difference in elevation to store excess water for generating power. Hydrogen storage does not require special conditions related to geography.
In addition, said Autrey, the bigger the scale, the more economical hydrogen. It’s cheaper to buy a few extra hydrogen storage tanks than to buy lots of batteries.
Find the best way for hydrogen storage
Clean hydrogen holds great promise as an energy source. A process called electrolysis, for example, can split water into hydrogen and oxygen. In the best world, the power of electrolysis would come from renewable energy sources, including solar, wind and geothermal.
However, there is one stubborn challenge: producing hydrogen more cheaply.
To address this, in 2021 the DOE announced the Energy Earthshots initiative, a series of six steps to support breakthroughs in clean energy technologies. First introduced was the Hydrogen Shot, an attempt to reduce the cost of hydrogen from $5 to $1 per kilogram within a decade—an 80 percent reduction.
As well as lowering the cost of producing clean hydrogen, “you have to think about how to move it and store it,” says Autrey, which is a step that could drive prices back up.
But finding the ideal medium for hydrogen storage has been elusive.
Hydrogen can be compressed into a gas, but it requires very high pressure—up to 10,000 pounds per square inch. Secure storage tanks require very thick steel walls or expensive space-grade carbon fiber.
What about cryogenic liquid hydrogen? It is a proven storage medium but requires and stores something extremely cold (-471 F, or -279.4 °C) so the peripheral energy costs are significant.
What seems most promising are molecules that are liquid, optimized for storing and releasing hydrogen. Jamie Holladay, an expert on sustainable energy, recently directed PNNL-led research on simpler and more efficient strategies for liquefying hydrogen.
Using liquids as storage media has the advantage of preserving existing energy infrastructure, including pipelines, trucks, rail and transport vessels, Gutierrez said.
The bicarbonate-format cycle
Want to bake a cake? Or store hydrogen energy? Baking soda could be the ticket. This light, inexpensive salt of sodium bicarbonate is non-toxic and abundant on Earth.
Not baking soda exactly. The PNNL team is investigating the long-studied hydrogen energy storage properties of the bicarbonate-format cycle. (Formate is a safe, light liquid organic molecule.)
Here’s how it works: Solutions of formate ions (hydrogen and carbon dioxide) in water carry hydrogen based on the non-corrosive alkali metal formate. The ions react with water in the presence of a catalyst. The reaction creates hydrogen and bicarbonate― the “baking soda” that Autrey admires for its zero environmental impact.
With a light, precise adjustment of pressure, the bicarbonate-formate cycle can be reversed. It provides an on-off switch for aqueous solutions which can alternately store or release hydrogen.
Prior to baking soda, the PNNL hydrogen storage team viewed ethanol as a liquid organic hydrogen carrier, the industry umbrella term for a storage and transport medium. Together, they developed a catalyst that releases hydrogen.
Catalysts are designer additives that speed up the processes used to make and break chemical bonds in an energy efficient way.
In May 2023, for a project related to the PNNL effort, EERE awarded OCOchem of Richland, Washington, $2.5 million in funding over two years to develop an electrochemical process that makes formic acid and formic acid from carbon dioxide. This process will bind carbon dioxide with hydrogen located in water’s iconic chemical bond, H2HI.
In the newly started partnership, PNNL will develop a way to release hydrogen from OCOchem products.
Hydrogen storage that ‘looks like water’
In the world of hydrogen storage research, the bicarbonate-formate cycle has been buzzing around for some time. After all, it is based on abundant, non-flammable and non-toxic materials.
The cycle is built on an aqueous storage solution so light it “looks like water,” says Autrey. “You can put out the fire with it.”
But for formate-bicarbonate salts to be a viable way of storing hydrogen energy, researchers still have to develop economically viable scenarios. So far, the technology stores only 20 kilograms per cubic meter of hydrogen, compared to the industry standard of 70 liquid hydrogen.
More fundamentally, says Autrey, researchers need a system-level understanding of the electrochemistry and catalysis required. In engineering terms, until recently, the notion of an applicable bicarbonate-format cycle had a low level of technical readiness.
“If we solve the catalysis problem,” he adds, “we can get some real interest.”
‘Incredible shiny thing’
On the plus side, the salt solution considered in PNNL releases hydrogen when reacting with water. They also operate at moderate temperatures and low pressures.
In theory, at least, as Autrey and Gutiérrez explain in their 2023 paper, the bicarbonate-format cycle represents a “viable eco-friendly alternative for storing and transporting energy” of hydrogen.
The baking soda idea also ties into what the 2023 paper calls “several pressing scientific challenges.”
Among them is how to make hydrogen storage media from excess carbon dioxide that is captured. And it even uses the same medium to store electrons, which promises a straight-forward fuel cell.
In addition, the PNNL work may provide insights for catalysis in the aqueous (aqueous) phase. For now, the PNNL team is using palladium as their candidate catalyst. Their efforts include finding ways to make rare metals more stable, reusable and long-lived.
Overall, the baking soda idea “is an amazing shiny thing” for hydrogen storage, says Autrey. “What’s interesting are the possibilities.”
