Direct ammonia synthesis by alkaline membrane based electrolysis

Project lead

Dr Gurpreet Kaur, Gurpreet.Kaur@csiro.au

Challenge

Recently, the electrochemical route of green hydrogen production from water has attracted worldwide attention due to the increasing availability of renewable energy sources. However, hydrogen storage and distribution are still dominating sectors.

Ammonia contains 17.6 wt.% of H₂ and can also be used as a hydrogen carrier. Ammonia has high volumetric energy density and is easier to store and transport. To produce green ammonia, current technologies are considering producing green hydrogen from water electrolysis, avoiding natural gas steam reforming. This helps to mitigate the significant carbon emissions (1.83 tCO₂/tNH₃ emitted by the current route). The hydrogen produced is then used in conventional reactors for ammonia synthesis. However, the process is still energy intensive as high temperatures (~450°C) and high pressures (~200 bar) are required for ammonia production with single-pass ammonia yields of only 15.5 vol%.

What we are doing

Biological nitrogen fixation process catalysed by nitrogenase enzyme can produce ammonia from N₂ at ambient conditions which is well known phenomenon.  We are translating this phenomenon in electrochemical systems. Using such systems, ammonia can be synthesized in a single reactor at milder process conditions including atmospheric pressure. The only feedstock for this process is water, nitrogen (from air) and a renewable source of electricity. In addition, no air separation units are required for N₂ feedstock.

The project will research and develop an electro-catalysts/electrochemical interface, other cell materials/cell fabrication/assembly, and perform electrolysis cell evaluation and results analysis. The CSIRO team efforts are to produce green ammonia production rates comparable to Haber Bosch recorded with novel developed catalysts.

Although ammonia synthesis by the electrochemical route can provide numerous advantages for a carbon free energy future, there are several challenges in the development of this technology that we will need to overcome. In the electrochemical ammonia synthesis process, hydrogen evolution reaction is more favourable than nitrogen reduction (being triple bond) at operating conditions, which results in very low ammonia selectivity.

We are working on the development of low-cost, efficient catalysts that could improve the selectivity for ammonia production in comparison to hydrogen production. Research work also includes the optimisation of process conditions such as applied voltages, temperature, pressure for higher ammonia formation rates. Notably, both H₂ and ammonia are carbon free fuels and technology have multiple advantages in various aspects.

Outcomes to date

Although ammonia synthesis by electrochemical route can provide numerous advantages for a carbon free energy future, there are several challenges in the development of this technology that will need to be overcome. In the electrochemical ammonia synthesis process, hydrogen evolution reaction is more favourable than nitrogen reduction (being triple bond) at the operating conditions which results in very low ammonia selectivity.

At CSIRO, we are working on the development of low-cost efficient catalysts that could improve the selectivity for ammonia production in comparison to hydrogen evolution reaction. Research work also includes the optimisation of the process conditions such as applied voltages, temperature, pressure for higher ammonia formation rates. Notably, both the products such as H₂ and ammonia are carbon free fuels and technology have multiple advantages in various aspects.

Lessons learned

Project finish date

June 2025

Relevant project publications

1. Ammonia as a Renewable Energy Transportation Media https://pubs.acs.org/doi/full/10.1021/acssuschemeng.7b02219
2. Engineering a solid-state metalloprotein hydrogen evolution catalyst- https://www.nature.com/articles/s41598-020-60730-y
3. Insights into nitrogenase bio electrocatalysis for green ammonia production https://doi.org/10.1002/cssc.202001433
4. Rhodium-molybdenum oxide electrocatalyst with dual active sites for electrochemical ammonia synthesis under neutral pH condition- https://doi.org/10.1016/j.jelechem.2021.115157
5. Green ammonia synthesis using CeO2/RuO2 nanolayers on vertical graphene catalyst via electrochemical route in alkaline electrolyte. https://doi.org/10.1039/D1NR06411H

HyResearch record

Electrochemical synthesis of green ammonia from water and air – HyResearch (csiro.au)