Direct ammonia synthesis by alkaline membrane based electrolysis
Around 180 million tons of ammonia is synthesised each year for utilization in various industries mostly in fertilizer industry and rest as a chemical in plastics, textile industry, and so on. For energy sector, ammonia is carbon free energy source and contains 17.6 wt.% of H2. Ammonia produced by using renewable energy sources can be used as an energy or hydrogen carrier. However, the current process of ammonia synthesis that requires fossil fuels as feedstock is very energy intensive requiring high temperature (~ 450 °C) and high pressure (~200 bar), and significantly contributes to global CO2 emissions.
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. The only feedstock for this process is water, nitrogen (from air) and a renewable source of electricity.
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.
The concept of electrochemical ammonia synthesis has been demonstrated in CSIRO labs and the project is in early stage of development. The project team is adopting different strategies to improve the ammonia formation rates. We are collaborating with Korean Research Institute of Chemical technology, Korea to develop alkaline based membranes for ammonia synthesis. We are also collaborating with RMIT, by having a PhD student working on this project, investigating specifically the low-cost catalysts for the ammonia synthesis process.
For more information, please contact Gurpreet.Kaur@csiro.au