Für den Inhalt der Angaben zeichnet die Projektleitung verantwortlich.
Dieses von der Gebert Rüf Stiftung geförderte Projekt wird von folgenden weiteren Projektpartnern mitgetragen: Ecole Polytechnique Fédérale de Lausanne, Nanophotonics and Metrology Laboratory; Scouting & Incubation, Advanced Materials & System Research, BASF Schweiz AG
Project no: GRS-039/16
Amount of funding: CHF 160'000
Duration: 04.2017 - 09.2018
Area of activity: Pilotprojekte, 1998 - 2018
Dr. Olivier Martin, Head of Lab
Ecole Polytechnique Fédérale de Lausanne
Nanophotonics & Metrology Lab
EPFL-STI-NAM, ELG 240
1015 Lausanne (Schweiz)
- olivier.martin@epfl. ch
The goal of this project is to establish an original framework to develop an energy efficient, environmental friendly and sustainable method for the synthesis of ammonia, one of the most commonly produced industrial chemicals. Indeed, the entire agro-food industry relies on ammonia to produce fertilizers in order to provide sufficient food to the world population. Ammonia (NH3) is obtained by splitting a nitrogen molecule N2; unfortunately, the two nitrogen atoms in that molecule are extremely strongly bound together, such that very high energy is required to break that bond and produce ammonia. Consequently, today, the synthesis of ammonia consumes approx. 2% of the world’s annual energy! On-going ammonia production requires both a very high pressure and a temperature, which are extremely energy greedy.
In this project, we aim at exploring a completely different route for splitting nitrogen molecules to produce ammonia, based on plasmon-assisted heterogeneous catalysis. This approach relies on two key phenomena. On the one side, nitrogen molecules will be adsorbed on a nanostructured surface, which will reorganize their energy landscape in a way such that the binding energy between both nitrogen atoms will decrease. This corresponds to the catalysis part and can be understood by a simple analogy: when a person is swimming freely in shallow water with all arms and legs stretched to float, it has a certain kinetic energy; when that person stands up on the ground in the water, its kinetic energy decreases. On the other side, we wish to harvest energy from light using plasmonic nanostructures in order to promote the nitrogen splitting process. Plasmonic nanostructures are made of specific metals such as gold, silver or aluminium. A metal is a good electric conductor because it possesses many free electrons that can be used to flow an electric current when a voltage is applied. In a plasmonic metal, this number of free electrons is so high that applying only light is sufficient to put the electrons in the metal in motion. By combining both effects, we do hope to be able to perform nitrogen splitting using much less energy than existing industrial processes.
What is special about the project?
This project aims at taking a completely fresh view on an existing industrial process by combining competences that stem from very different horizons and include nanotechnology, surface chemistry and electrochemistry.
During the reporting period of the project, we have successfully developed an alternative route for ammonia synthesis through nitrogen splitting at room temperature under atmospheric pressure using plasmonic aluminium nanotriangles (AlNTs) and titanium dioxide (TiO2) where the AINTs were fabricated using colloidal lithography, a technology that can be used on full wafers. In a first step, optical and photocatalytic properties of the photoelectrodes were well characterized. The UV plasmonics of the AlNTs significantly increases the number of charge carriers in the TiO2 photoelectrodes which is attributed to the plasmonic near field coupling as the surface plasmon resonance of the AlNTs matches well with the band gap energy of the TiO2. Under resonant conditions, the surface plasmon oscillation of the AlNTs concentrates the electromagnetic energy near the edges of the triangles, where it penetrates into the TiO2 and increases the charge carrier generation. The AlNTs embedded TiO2 photoelectrode shows a 0.17 µM h-1 ammonia production which represents a ~3 fold increase compared to bare TiO2 (0.06 µM h-1) suggesting a successful nitrogen splitting at room temperature under atmospheric pressure. The quantum efficiency of the AlNTs-TiO2 photoelectrode is ~0.3% which is significantly higher than earlier reported methods.
i) Optimized photoelectrodes and ii) Synthesis of ammonia in solution are the two milestones achieved at this stage. The photoelectrodes systems we have developed is very new and we are currently in discussion with the EPFL Technology Transfer Office to assess whether it could be patented. Scientific publications will follow afterwards. Further work, the ammonia synthesis in the gas phase using visible light is progressing. To boost that part of the project, we have recently invested using our own internal budget into a mass spectrometer, which will allow us to obtain more quantified information on the nitrogen splitting mechanism studied by analyzing the different by-products formed during the reaction.
Persons involved in the project
Last update to this project presentation 03.07.2019