Liquid metal catalyses ammonia production

Ammonia is used in fertiliser and is set to have a role in clean energy as a carrier to transport hydrogen. However, the global production of ammonia consumes over two per cent of global energy and produces up to two per cent of global carbon emissions.

RMIT research fellow and study lead author, Dr Karma Zuraiqi, said their greener alternative used 20 per cent less heat and 98 per cent less pressure than the Haber-Bosch process currently used for splitting nitrogen and hydrogen into ammonia.

“Ammonia production worldwide is currently responsible for twice the emissions of Australia. If we can improve this process and make it less energy intensive, we can make a large dent in carbon emissions,” Zuraiqi, from RMIT’s School of Engineering, said in a statement. 

Results of the RMIT-led study published in Nature Catalysis show their low-energy approach to be as effective at producing ammonia as the current gold standard by relying more on effective liquid metal catalysts and less on the force of pressure. 

“The copper and gallium we use is also much cheaper and more abundant than the precious metal ruthenium used as a catalyst in current approaches,” said Zuraiqi. “These advantages all make it an exciting new development that we’re keen to take further and test outside the lab.” 

The team, including RMIT’s Professor Torben Daeneke, is said to be at the forefront of harnessing the properties of liquid metal catalysts for ammonia production, carbon capture and energy production. 

This latest study showcased their new technique by creating tiny liquid metal droplets containing copper and gallium as the catalyst to break apart nitrogen and hydrogen. 

“Liquid metals allow us to move the chemical elements around in a more dynamic way that gets everything to the interface and enables more efficient reactions, ideal for catalysis,” said Daeneke. “Copper and gallium separately had both been discounted as famously bad catalysts for ammonia production, yet together they do the job extremely well.”  

Tests revealed gallium broke apart the nitrogen, while the presence of copper helped the splitting of hydrogen, combining to work as effectively as current approaches at a fraction of the cost. 

“We essentially found a way to take advantage of the synergy between the two metals, lifting their individual activity,” said Daeneke. 

RMIT is now leading commercialisation of the technology, which is co-owned by RMIT and Queensland University of Technology.