Scientists at the RIKEN Center for Emergent Matter Science in Japan have found a way to safely and efficiently store ammonia using a chemical reaction. They used a perovskite called ethylammonium lead iodide (EAPbI3), which interacts with ammonia at room temperature, transforming its structure and storing the ammonia inside. Remarkably, the stored ammonia can be easily recovered by mildly heating the compound, and the perovskite can be reused for continuous storage and extraction cycles.
Japanese scientists have discovered a compound, lead ethylammonium iodide, that can safely and efficiently store and release ammonia. This finding has potential for ammonia’s role as a carbon-free hydrogen carrier, contributing to the transition to a decarbonized society.
Scientists at the RIKEN Center for Emergent Matter Science (CEMS) in Japan have discovered a compound that uses a chemical reaction to store ammonia, potentially offering a safer and simpler way to store this important chemical.
In order for society to transition from carbon-based energy to hydrogen-based energy, we need a safe way to store and transport hydrogen, which is itself highly flammable. One way to do this is to store it as part of another molecule and extract it as needed. Ammonia, chemically written as NH3, is a good hydrogen carrier because three hydrogen atoms are packed into each molecule, with almost 20% of ammonia being hydrogen by mass.
The problem, however, is that ammonia is a highly corrosive gas, making it difficult to store and use. Currently, ammonia is generally stored by liquefaction at temperatures well below freezing in pressure-resistant containers. Porous compounds can also store ammonia at room temperature and pressure, but the storage capacity is low and ammonia is not always easily obtained.
A research team led by Masuki Kawamoto of RIKEN CEMS focused on the perovskite ethylammonium lead iodide (EAPbI3), chemically written as CH3CH2NH3PbI3. They found that its one-dimensional columnar structure undergoes a chemical reaction with ammonia at room temperature and pressure and dynamically transforms into a two-dimensional layered structure called lead hydroxide iodide, or Pb(OH)I. EAPbI3 can safely store corrosive ammonia gas as a nitrogen compound in a process that is much cheaper than liquefaction at −33 °C (−27.4 °F) in pressure vessels. More importantly, the process of recovering stored ammonia is just as simple.
“To our surprise, ammonia stored in ethylammonium lead iodide can be easily extracted by heating it slightly,” says Kawamoto. The stored nitrogen compound undergoes a reverse reaction at 50 °C (122 °F) under vacuum and returns to ammonia. This temperature is much lower than the 150 °C (302 °F) or more needed to extract ammonia from porous compounds, making EAPbI3 an excellent medium for handling corrosive gases in a simple and cost-effective process.
Furthermore, after returning to a one-dimensional columnar structure, the perovskite can be reused, allowing repeated storage and extraction of ammonia. An added bonus was that the normally yellow compound turned white after the reaction. According to Kawamoto, “the compound’s ability to change color when ammonia is stored means that color ammonia-based sensors can be developed to determine the amount of ammonia stored.”
The new storage method has several uses. In the short term, scientists have developed a safe method of storing ammonia, which already has many uses in society, from fertilizers to medicines to textiles. “In the long run,” says co-author Yoshihiro Ito of RIKEN CEMS, “we hope that this simple and effective method can be part of the solution to achieving a decarbonized society through the use of ammonia as carbon-free hydrogen carrier.”
