NitroFix, an Israeli cleantech startup founded in 2022, develops the technology to make ammonia by electrochemically reducing nitrogen using its unique polyoxometalate molecular catalysts. This technology allows for the on-site production of ammonia using water, air, and renewable electricity and is easily scalable to fit the needs of any size operation.
Challenges: green ammonia
Ammonia (NH₃) is a crucial compound for agriculture. In 2021, the global production of ammonia was 185 million metric tons, with over 80% being used for fertilizer production. As the global population increases, so does the demand for ammonia.
The primary method of ammonia production is the Haber-Bosch process, which converts hydrogen (H₂) and nitrogen (N₂) into ammonia. World-scale ammonia synthesis plants can produce up to 5,000 metric tons per day. They are usually situated in remote areas with cheap natural gas. The produced ammonia is transported considerable distances to customers and contributes to carbon emissions.
The Haber-Bosch process requires very high purity hydrogen and nitrogen and high temperature and pressure (above 450 ºC and 200 bar, respectively), which are highly optimized for the iron-based catalysts to attain significant yields of ammonia. The energy-intensive nature of the process results in the consumption of about 2% of worldwide fossil fuels and an annual emission of over 420 million tons of carbon dioxide (CO₂). The production of ammonia contributes to 1.5% of global greenhouse gas emissions.
Therefore, there is an urgent need to develop technologies for ammonia synthesis in a sustainable manner. The utilization of renewable energy to convert nitrogen into ammonia represents a promising approach for the production of green ammonia.
NitroFix Technology
NitroFix has developed the technology to make ammonia using nitrogen and water in an electrochemical cell powered by renewable electricity. The electrochemical synthesis of ammonia is conducted at low pressure and ambient temperature. The core technology of NitroFix is the unique polyoxometalate molecular catalysts, which selectively catalyze the electrochemical reduction of nitrogen to ammonia. The ammonia yield rate is 1-2 nmol sec⁻¹ cm⁻² with a moderate faradaic efficiency of 25–30%. The performance can be improved further by optimizing the design of the electrochemical cell system, molecular catalysts, and electrolyte compositions.
NitroFix ammonia
The diagram below illustrates the NitroFix electrochemical cell for the electrocatalytic reduction of nitrogen to ammonia.
A proton-permeable membrane separator separates the cathodic and anodic chambers in an electrochemical cell. In the cathodic chamber, a cathode and reference electrode are immersed in a catholyte. In the anodic chamber, an anode is immersed in an anolyte. The electrodes are connected to a power source capable of applying a voltage between the cathode and anode.
Cathode is typically made of copper (Cu) foam or nickel (Ni) mesh, and anode is made of platinum (Pt). The catholyte consists of a low-concentration polyoxometalate catalyst (e.g., 0.5 millimolar), a high-concentration sodium trifluoromethanesulfonate (NaCF₃SO₃) (e.g., 0.5 molar), a polyethylene glycol (PEG-400) solvent, and 1 vol% of water. Anolyte is water, which acts as a proton donor. The membrane separator prevents the transmission of substances other than protons between the cathodic and anodic reaction chambers.
The polyoxometalate catalyst, such as K{SiFe₃W₉}, is easy to synthesize and shows thermal and oxidative stability. Its intrinsic properties may be modified easily, and it can be used with excellent efficiency in transformations involving electron transfer.
Process of NitroFix electrochemical ammonia synthesis
The diagram below illustrates the process of electrochemical reduction of nitrogen to ammonia with the polyoxometalate molecular catalyst.
During operation, pressured nitrogen is fed into the cathodic chamber. A voltage is applied between the cathode and anode.
At the anode, water undergoes electrochemical oxidation to generate protons (H⁺) and oxygen (O₂):
2H₂O → O₂ + 4H⁺ + 4e⁻
Protons migrate across the membrane separator to maintain charge neutrality. They enter the catholyte and regenerate the proton carrier by protonation of the proton acceptor. O₂ is removed from the anodic chamber.
At the cathode, the current flow causes the reduction of nitrogen to ammonia through the following electrochemical processes:
Performance of NitroFix electrochemical ammonia synthesis
The electrochemical reduction of nitrogen to ammonia with the polyoxometalate catalyst K{SiFe₃W₉} has been evaluated in an electrochemical cell without a membrane. Under 1 bar of N₂ operated at −1.3 V versus the stand hydrogen electrode (SHE), the ammonia yield rate is 1-2 nmol sec⁻¹ cm⁻² with a moderate faradaic efficiency of 25–30% for a duration of over 10 hours. The performance can be further improved by using an electrochemical cell with a membrane that separates the cathode and anode chambers. Moreover, increasing the pressure of feeding nitrogen can increase the solubility of nitrogen in the catholyte and improve the ammonia yield rate.
NitroFix Patent
- WO2023100180A3 Electrochemical reduction of nitrogen to ammonia catalyzed by polyoxometalates
NitroFix Technology Applications
Agriculture
Green ammonia can be used as a carbon-neutral fertilizer, significantly reducing the carbon footprint of farming. Using green ammonia for fertilizer could drive down farming’s carbon footprint by as much as 90% for corn and small grain crops.
Transportation fuel
Green ammonia can be used as a transport fuel, replacing highly polluting gasoline, diesel, and propane to run engines, generators, and turbines. It has applications in transportation, including heavy goods vehicles, trains, aviation, and shipping.
Energy storage
Green ammonia has the potential to be used for large-scale, long-term energy storage. It has nine times the energy density of Li-ion batteries and three times that of compressed hydrogen, making it a competitive option against electrochemical batteries, pumped hydro, and capacitors to balance consumption and renewable generation. Countries including Japan, Australia, the Netherlands, and the United Kingdom have national plans to use green ammonia to store (and export) their renewable energy surpluses.
NitroFix Products
NitroFix is developing its electrochemical cells and systems for on-site green ammonia production. The company aims to develop a modular and decentralized production platform to produce 100 to 100,000 tons of ammonia per year.
NitroFix Funding
NitroFix has raised a total of $3.6M in funding over two Seed rounds. Their latest Seed funding was raised on Jul 14, 2023.
NitroFix Investors
NitroFix is funded by 6 investors:
Zero Carbon Capital and UM6P Ventures are the most recent investors.
NitroFix Founder
Ophira Melamed, Meital Alon, Yehuda Borenstein, and Ronny Neumann are Co-Founder.
NitroFix CEO
Ophira Melamed is CEO.
