Researchers discover a safe, easy, and affordable way to store and recover hydrogen

Researchers at the RIKEN Center for Emerging Materials Science (CEMS) in Japan have discovered a compound that uses a chemical reaction to store ammonia, which may provide a safer and easier way to store this important chemical.

This discovery was published in Journal of the American Chemical Society On July 10, it is not only possible to store ammonia safely and conveniently, but also allows the important hydrogen to be carried. This result should help pave the way to a carbon-neutral society with a practical hydrogen economy.

For society to make the shift from carbon-based to hydrogen-based energy, we need a safe way to store and transport hydrogen, which itself is highly combustible. One way to do this is to store it as part of another molecule and extract it as needed. Ammonia, written chemically as NH₃makes a good hydrogen carrier because three hydrogen atoms are packed into each molecule, with approximately 20% of ammonia being hydrogen by weight.

However, the problem is that ammonia is a highly corrosive gas, which makes it difficult to store and use. Currently, ammonia is generally stored by liquefying it 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 cannot always be easily recovered.

The new study reports the discovery of perovskite, a material with a characteristic repeating crystalline structure, that can readily store ammonia and also allows for its easy and complete recovery at relatively low temperatures.

The research team led by Masuki Kawamoto at RIKEN CEMS focused on perovskite ethylammonium lead iodide (EAPbI).₃), chemically written as CH₃CH₂New Hampshire₃PbI₃. They found that its one-dimensional columnar structure undergoes a chemical reaction with ammonia at room temperature and pressure, dynamically transforming into a two-dimensional structure called lead iodide hydroxide, or Pb(OH)I.

As a result of this process, ammonia is stored within a layered structure through chemical conversion. Thus, the EAPbI₃ Corrosive ammonia can be safely stored as a nitrogen compound in a much cheaper process than liquefaction at -33°C (-27.4°F) in pressurized containers. More importantly, the process for recovering stored ammonia is very simple.

“To our surprise, the ammonia stored in ethylammonium lead iodide can be easily extracted by gently heating it,” says Kawamoto. The stored nitrogen compound undergoes a reverse reaction at 50 °C (122 °F) under vacuum and reverts to ammonia. This temperature is well below the 150 °C (302 °F) or more needed to extract ammonia from porous compounds, making EAPbI₃ An excellent medium for dealing with corrosive gases in a simple and cost effective process.

In addition, after returning to a one-dimensional columnar structure, the perovskites can be reused, allowing for repeated storage and extraction of ammonia. An added bonus was that the naturally yellow compound turned white after the reaction. According to Kawamoto, “The compound’s ability to change color when ammonia is stored means that colorimetric ammonia sensors can be developed to determine the amount of ammonia stored.”

The new storage method has many uses. In the short term, researchers have developed a safe way to store ammonia, which already has multiple uses in society, from fertilizers to medicines to textiles. “In the long term, we hope that this simple and effective method can be part of the solution to achieving a carbon-neutral society through the use of ammonia as the carrier carbon-free hydrogen,” says co-author Yoshihiro Ito of RIKEN CEMS.

This research will help achieve the 2016 Sustainable Development Goals (SDGs) set by the United Nations, especially Goal 7: Clean, Affordable Energy and Goal 13: Climate Action.