The use of HEAs for ammonia synthesis is a quite innovative approach: the first article, published in 2021 [1], showed 11.4 µg h–1 cm–2 NH3 production rate with CoCuFeNiRu. The production rate achieved in TELEGRAM adopting a CoCrFeMnNi alloy is 9.8 µg h–1 cm–2, therefore comparable with the literature, but avoiding the use of Ru as precious material. Even higher rate (21.4 µg h–1 cm–2) has been achieved using non-aqueous Li based electrolyte.
Nanostructured catalysts have been largely employed in literature for ammonia synthesis. Fe3O4/Fe catalysts [2] exhibit production rate of 0.07 µg cm-2 h-1 and 8% faraday efficiency. The values obtained in TELEGRAM (1.22 µg cm-2 h-1 and 20%) are both higher, benefitting from an electrochemical activation procedure. A paper using Au nanoparticles on carbon fiber [3] claims for an excellent performance with rate of 40.6 µg h−1 mg−1 and great efficiency of 31.3%. In TELEGRAM, with Mo-Au catalysts on hydrophobic carbon fiber, values beyond the state of the art have been obtained, with 41% faraday efficiency. Recently, positive cooperation of metal single-atom (SA) catalysts (Rh, Ru and Co) has been demonstrated, with a pressurized membrane-separated electrolysis system. Under pressurized conditions of 55.7 bar of N2, the Rh SA catalyst displayed a NH3 yield rate of 74.15 μg h−1 ·cm−2, a value 7.3-fold higher than that obtained at the ambient conditions [4]. However, the combined role of temperature and pressure in mild conditions (pressure < 10 bar) proposed in the TELEGRAM project, has not been previously studied in literature. In the case of Rh SA the ammonia production rate at 10 bar is increased by a factor 1.7; a pressure of 30 bar is required to increase the rate by a factor 3.75. The combined increase of both temperature (75°C) and pressure (5 bar), adopted in TELEGRAM, leads to an increase of ammonia production rate by more than a factor 5, while keeping the overall temperature and pressure conditions in a mild operating range.
The possibility to produce green NH3 is expected to have political impact, contributing to establish a solid European innovation base and to build a sustainable energy system, through the development of two enabling technologies in the field of electrochemistry: the synthesis of ammonia and its use as a fuel in the DAFC. We may also expect an environmental impact since the project has involved the development of a knowledge that can be used for recycling ammonia from wastewater. The two technologies addressed by the TELEGRAM project, are still at a nascent stage. Therefore, there is a strong impact related to technical and innovation aspects. The basic knowledge the TELEGRAM consortium has acquired is fundamental to collect scientific proofs of the technological feasibility of its basic concept and to build a know how crucial for designing better performing devices. The knowledge is being used to create a European team with basic skills on catalysts and electrochemical systems that can develop further research, assessing innovative strategies to produce fuels from renewable energy sources. In the last five years, among the 10500 papers published on nitrogen reduction, less than 10% have been produced in EU countries. This indicates there is a lack of knowledge in the field in EU, and the TELEGRAM consortium is contributing to fill this gap, producing reliable data. The project has also attracted young researchers, with 3 PhD students and 4 Post Doc researchers working on the project. Thus TELEGRAM is contributing to create the next generation of European scientists who will boost the transition of Europe to a sustainable energy system.
[1]Zhang, D. et al. Adv. Funct. Mater. 2021, 31, 2006939.
[2]Hu L. et al, ACS Catalysis 2018, 8, 9312.
[3]Zhang, J. et al, Adv. Science 2020, 7, 2002630.
