At Low Temperatures, a New Catalyst can Produce Hydrogen from Ammonia

When hydrogen gas is burned in the presence of oxygen, it produces a lot of energy, but unlike fossil fuels, it does not emit harmful greenhouse gases. Unfortunately, the majority of hydrogen produced today is derived from natural gas or fossil fuels, which increases the carbon footprint.

With the help of metal catalysts such as nickel, ammonia, a carbon-free resource, can be split into nitrogen and hydrogen gas (Ni). However, these reactions frequently necessitate extremely high operating temperatures. Scientists have now developed a highly efficient calcium imide (CaNH)-supported Ni catalyst that can decompose ammonia at temperatures 100°C lower than those required by conventional Ni catalysts. This promising new catalyst could help us get closer to producing hydrogen fuel in a sustainable manner.

Because of the current global climate emergency and our rapidly dwindling energy resources, people are looking for cleaner alternatives such as hydrogen fuel. When hydrogen gas is burned in the presence of oxygen, it produces enormous amounts of energy while emitting no harmful greenhouse gases, unlike fossil fuels. Unfortunately, the majority of hydrogen fuel produced today is derived from natural gas or fossil fuels, which increases its carbon footprint.

Now scientists developed a highly efficient calcium imide (CaNH)-supported Ni catalyst that can decompose ammonia at temperatures 100°C lower than what conventional Ni catalysts require.

Ammonia (NH3), a carbon-neutral hydrogen compound, has recently received a lot of attention due to its high energy density and high hydrogen storage capacity. It can be decomposed to produce nitrogen and hydrogen gases. Ammonia is easily liquified, stored, and transported, and it can be converted into hydrogen fuel when needed. However, producing hydrogen from ammonia is a slow reaction with high energy requirements. Metal catalysts are frequently used to speed up production, which also helps reduce overall energy consumption during hydrogen production.

According to recent research, nickel (Ni) is a promising catalyst for ammonia splitting. Ammonia adsorbs on the surface of Ni catalysts, causing the bonds between nitrogen and hydrogen in ammonia to break and the gases to be released as individual gases. However, obtaining a good ammonia conversion using a Ni catalyst frequently necessitates extremely high operating temperatures.

Breaking ammonia: A new catalyst to generate hydrogen from ammonia at low temperatures

Ammonia (NH3), a carbon-neutral hydrogen molecule, has received a lot of attention recently because of its high energy density and hydrogen storage capacity. It is capable of decomposing and releasing nitrogen and hydrogen. Ammonia is easily liquefied, stored, and transported, and it can be converted into hydrogen if needed. Hydrogen production from ammonia, on the other hand, is a time-consuming and energy-intensive process. Metal catalysts are frequently used in hydrogen synthesis to increase output while reducing total energy consumption.

In a recent study published in ACS Catalysis, a team of Tokyo Tech researchers led by Associate Professor Masaaki Kitano described a solution to the problems encountered by Ni-based catalysts. They created a cutting-edge calcium imide (CaNH)-supported Ni-catalyst that can convert ammonia at low operating temperatures. Dr. Kitano elaborates, “Our goal was to create a highly active, energy-efficient catalyst. The addition of the metal imide to the catalyst system not only improved its catalytic activity but also assisted us in elucidating the enigmatic working mechanism of such systems.”

The researchers discovered that the presence of CaNH caused the formation of NH2- vacancies (VNH) on the catalyst’s surface. These active species improved the catalytic performance of the Ni/CaNH catalyst at reaction temperatures that were 100°C lower than those required for the operation of Ni-based catalysts. In order to understand what is happening on the catalyst surface, the researchers also created computational models and performed isotope labeling.

The calculations proposed a Marsavan Krevelen mechanism involving ammonia adsorption on the CaNH surface, activation at the NH2-vacancy sites, nitrogen and hydrogen gas formation, and finally regeneration of vacancy sites aided by Ni nanoparticles.

The highly active and long-lasting Ni/CaNH catalyst can be successfully used to generate hydrogen gas from ammonia. This study’s insight into the mechanism of catalysis can also be used to develop a new generation of catalysts. “As the entire world works together to build a sustainable future,” Dr. Kitano concludes, “our research is aimed at resolving the hiccups encountered on our way to a cleaner hydrogen fuel economy.”