Research: Baking Soda Used for Hydrogen Storage
A Pacific Northwest National Laboratory study found that electro- and thermo-chemical bicarbonate-formate cycling can be harnessed to store and release hydrogen.
Pacific Northwest National Laboratory (PNNL) researchers have discovered that a baking soda solution could store and transport hydrogen energy.
Hydrogen molecules. Image used courtesy of Pexels
Baking soda, a longtime household staple, is a sodium bicarbonate compound, a mild salt containing a sodium cation and a bicarbonate anion. The bicarbonate-formate cycle features non-toxic, non-flammable, and abundant materials—all conditions of a promising hydrogen storage application.
Hydrogen, the world’s simplest and most abundant element, is in nearly 75% of the universe's matter. Its high energy content and role as an effective energy carrier make it an increasingly attractive resource in the renewable energy market because it entails no emissions—prompting the rise of hydrogen storage and fuel cell technologies for stationary and portable power and transportation applications.
Still, large-scale hydrogen storage deployment is hindered by a few key challenges. Its low ambient temperature density means it has a low energy per unit volume, per the Department of Energy (DOE), requiring more advanced storage methods accommodating higher energy density. Furthermore, while hydrogen is non-toxic and safer to handle than other standard fuels, it can ignite more easily and has a broad range of flammable concentrations in air, from 4% to 74%.
Key Research Findings
PNNL’s researchers found that the challenges of handling molecular hydrogen can be addressed with liquid hydrogen carriers. In a study published in Green Chemistry, the team explored the bicarbonate-formate cycle, in which aqueous solutions of formate ions can be used as hydrogen and energy carriers.
The researchers explain in the abstract that these solutions feature abundant elements. They’re also non-flammable, unlike common liquid organic carriers. And they can convert to oxide forms when reacting with water to produce hydrogen (electrons) under moderate temperatures.
The bicarbonate-formate cycle’s thermodynamic characteristics enable a combination of electrochemical and thermochemical operations. It also presents an opportunity to couple carbon dioxide capture with energy and hydrogen storage.
Despite this theoretical promise, the researchers said more studies would be needed to determine feasible conditions for using formate/bicarbonate salts for hydrogen energy storage.
A visualization of how the electrochemical formate-bicarbonate cycle can store and release energy. Image used courtesy of PNNL (Creative Commons license)
PNNL notes that water solutions of formate ions (CO2 and hydrogen) can carry hydrogen based on a non-corrosive alkali metal formate. With a catalyst, the ions then react with the water and produce hydrogen and bicarbonates, thus the role of baking soda.
By adjusting pressure, the researchers could reverse the bicarbonate-formate cycle, enabling an aqueous solution capable of alternating between storing and releasing hydrogen.
There are still limitations to the findings, despite their theoretical feasibility. Formate-biocarbon salts only store hydrogen at 20 kilograms (kg) per cubic meter, less than the 70-kg industry standard of liquid hydrogen, according to PNNL.
The researchers wrote that more integration of electrochemistry and heterogeneous catalysis disciplines would be required to address challenges in advancing the bicarbonate-formate system as a feasible alternative to storing and transporting energy.
Overall, the study points to a unique cycle that can store and release hydrogen—which will be necessary when hydrogen production costs fall by 80%. The researchers noted that given the economic advantages and stability of earth-abundant salts, the cost of grid-scale energy storage could be reduced by 90%, enabling medium-/long-duration energy storage.
Capturing and using CO2 in the bicarbonate-formate cycle can also be useful in carbon capture and removal technologies.
A Similar Project With OCOchem
Relatedly, PNNL is also working to develop methods to release hydrogen from products by Washington-based startup OCOchem, which recently received a $2.5 million DOE grant for a two-year project.
The project aims to develop an electrochemical process to make formate and formic acid from CO2—in which CO2 would bind with the hydrogen in H2O, the chemical formula for water. PNNL is working on methods to release hydrogen from the formic acid safely.
OCOchem was one of 22 projects receiving nearly $42 million from the DOE to advance clean hydrogen production, storage, and deployment.