Researchers at the RIKEN Center for Emergent Matter Science (CEMS) in Japan have reported a simple and affordable perovskite-based way to store ammonia, an important chemical in a range of industries.
Ammonia is widely used across industries ranging from textiles to pharmaceuticals and is an important component in the manufacture of fertilizers. For its current use, ammonia is stored in pressure-resistant containers after liquefying it at temperatures of -27 Fahrenheit (-33 degrees Celsius). Alternate methods of storing ammonia in porous compounds have been explored. The storage and retrieval process can be achieved at room temperature, but the storage capacity of these compounds is limited. The research team, led by Masuki Kawamoto at RIKEN CEMS, has found that perovskites can also serve as an excellent medium for the storage and retrieval of ammonia.
Kawamoto's team found that the perovskite ethyl ammonium lead iodide (EAPbI3) reacts with ammonia at room temperature and pressure to make lead iodide hydroxide, or Pb(OH)I. Ethyl ammonium lead iodide has a one-dimensional columnar structure but, after reacting with ammonia, forms a two-dimensional layered structure.
Ammonia is a highly corrosive gas, but the chemical reaction with the perovskite allows for its safe storage that does not need any special equipment to store it either. The retrieval process is also very straightforward. Under vacuum, ethyl ammonium lead iodide can be heated to 122 Fahrenheit (50 degrees Celsius) to release ammonia gas.
In comparison, ammonia stored in porous compounds needs temperatures around 302 Fahrenheit (150 degrees Celsius) for recovery.
The discovery of the role of perovskite could be very important since it also offers a way to store hydrogen. Each molecule of ammonia packs three atoms of hydrogen and packing 20 percent of the weight of the molecule.
On its own, hydrogen is highly combustible, but ammonia does not combust easily, making it a good medium to store it until needed.
The perovskite-ammonia reaction is fully reversible, and the perovskite can be reused to store ammonia again after retrieval is completed. Interestingly, the perovskite also changes color to white when it stores ammonia and returns to its original yellow after ammonia is retrieved. Scientists can exploit this feature to make color-based sensors to determine the amount of ammonia stored in the perovskite.
A simple and affordable method where hydrogen can be extracted on-site and in the required amounts can pave a quicker way toward a hydrogen-based economy in the near future.
