Dioxycle, a French-American climate tech startup founded in 2021, develops electrolyzer technology that uses a CO₂-rich solvent from, for example, a Direct Air Capture unit or an industrial exhaust CO₂ capture system to turn CO₂ into valuable products like carbon monoxide, ethylene, methanol, and ethanol. These products can be further transformed into drop-in fuels. By converting CO₂ emissions into useful products, Dioxycle aims to decarbonize industries with unavoidable CO₂ emissions in their processes.
Challenges: carbon emissions
Since the early 1900s, carbon dioxide (CO₂) levels in the atmosphere have increased by 50% due to human activities. When fossil fuels (such as coal, oil, and natural gas) are burned for energy production, transportation, and industrial processes, CO₂ is released into the atmosphere. This excess CO₂ acts as a greenhouse gas, trapping heat and causing the air and ocean temperatures to rise. CO₂ emissions play a crucial role in driving climate change.
This warming effect has caused the global average temperature to rise by about 1.1 ºC since the pre-industrial period. This has led to rising in the frequency and intensity of extreme weather events, melting of polar ice caps and glaciers and rising sea levels, shifts in species ranges and increased risk of species extinction, agriculture and food security, and ocean acidification.
To mitigate these impacts, the Paris Agreement aims to limit global warming to well below 2 ºC above pre-industrial levels. The Intergovernmental Panel on Climate Change (IPCC) estimates that a “carbon budget” of about 500 GtCO₂, which corresponds to about ten years at current emission rates, provides a 66% chance of limiting global warming to 1.5 ºC.
Dioxycle develops electrolyzer technology that turns CO₂ into valuable products at low temperatures. The electrolyzer inputs a CO₂-rich solvent stream that can be from a Direct Air Capture unit, a seawater CO₂ capture system, or an industrial exhaust CO₂ capture system and reduces CO₂ at cathodes to valuable products, such as carbon monoxide (CO), methane (CH₄), ethylene (C₂H₄), propylene, dimethyl ether, ethanol, propanol, formic acid, as well as other achievable products, such as alkane, alkene, carboxylic acid, alcohol, aldehyde, or ketone.
The electrolyzer stack comprises a plurality of cells arranged in a stack. Each electrolyzer cell has a membrane electrode assembly (MEA) between two polar plates. The membrane selectively allows the flow of reactants across the membrane from the cathode or anode to the opposite electrode. The diagram below depicts the structure of an Dioxycle electrolyzer cell.
The electrolyzer cell includes the following components:
- Anode and cathode bipolar plates
The bipolar plates include inlet and outlet ports. It also has flow patterns to direct the flow of gasses and reactants in electrodes. They are made of stainless steel for conducting electricity. The polar plates are coated with Ti, Cr, Nb, Ni, Fe, or Au to minimize contact resistance and improve chemical resistance.
- Gas diffusion layers
Gas diffusion layers (GDLs) ensure a uniform distribution of reactive gasses on the surface of the electrodes and the transport of electrons from the external electrical circuit. Gas diffusion layers are made of porous carbon-based or metal based materials.
Metal-based porous GDLs are selected from titanium, stainless, and nickel which are in the form of mesh, frit, or foam.
The catalysts are embedded in, dispersed through, or deposited on the porous gas diffusion layer to catalyze chemical reactions on the electrodes.
The materials of catalysts are metal compounds, molecular species, carbon compounds, ionomers, or metal organic frameworks.
Metal catalysts include Ag, Au, Zn, Cu, Ir, Pt, Fe, Ni, Co, Mn, Sn, Bi, Pd, Pb, Cd, Ru, Re, Rh, as well as their alloys. They are nanoparticles, nanowires, or nano powder. Molecular catalysts include metal porphyrins, metal phthalocyanines, and metal bipyridine complexes.
- Membrane separator
The membrane separates electrodes and selectively mitigates the crossover of products/gasses between them.
The membranes are polymer-electrolyte membranes, such as anion-exchange membranes (AEMs), cation exchange membranes (CEMs), and bipolar exchange membranes.
A CEM contains anion groups, such as sulfonate, phosphonate, and carboxylate. Commercially available CEMs include Nafion® and Aquivion®.
A bipolar exchange membrane comprises CEMs and AEMs mentioned above. Commercially available bipolar exchange membranes include Fumasep® FBM and Xion.
- Cathodic input fluid
The cathodic input fluid provides CO₂ to be electrochemically reduced at the cathode. It is a CO₂-rich solvent stream which contains dissolved salts, such as Na(HCO₃)₂, Na₂CO₃, KOH, and NaCl. The presence of ions favors the ion-conducting activity of the ion-conducting interface at the membrane.
- Anodic input fluid
The anodic input fluid provides water or hydroxide ions to be electrochemically oxidized at the anode. It is an aqueous solution containing dissolved salts such as Na(HCO₃)₂, Na₂CO₃, NaCl, KOH, and Na₂SO₄.
How Dioxycle electrolyzer work?
During operation of the electrolyzer, reduction reactions occur on the cathodic electrode, while oxidation reactions take place on the anodic electrode.
CO₂ in the cathodic fluid is reduced to valuable products, such as carbon monoxide (CO), methane (CH₄), ethylene (C₂H₄), propylene, dimethyl ether, ethanol, propanol, formic acid, as well as any other achievable alkane, alkene, carboxylic acid, alcohol, aldehyde, or ketone (see US11655551B2 for details). Here, we illustrate the electrolyzer cell’s production of CO and ethylene as gaseous byproducts.
When the cathodic and anodic fluids are neutral or alkaline, the chemical reactions occurring on the electrodes are depicted in the diagram below.
When the cathodic and anodic fluids are acidic, the chemical reactions occurring on the electrodes are depicted in the diagram below.
The Dixoycle’s electrolyzer is particularly advantageous because it is easy to separate the gaseous products, such as CO and ethylene, from the unreacted CO₂ in the fluid, due to the lower solubility of these gaseous products compared to that of CO₂. The unreacted CO₂ can be recycled into the electrolyzer after pressurization.
- US11655551B2 Electrolyzer assembly comprising an insulating layer
- US11519089B1 Methods and systems for automated optimization of COx electrolysis reactor
- US20230010993A1 Carbon dioxide extraction electrolysis reactor
Global ethylene market
In the past few years, the global market for ethylene has grown steadily. The market was worth USD 166,520 million in 2019, and it is expected to be worth USD 245,005 million by 2027, growing at a CAGR of 5.6%. The ethylene market is driven by things like a growing population, better living conditions, more uses, and a rise in demand from emerging economies. Ethylene is mostly in demand because of all the ways it can be used in industries like packaging, auto, textiles, construction, and agrochemicals. Over 50% of the world’s demand for ethylene comes from the Asia-Pacific region. This trend is expected to continue as the region’s economy continues to grow.
Dioxycle plans to build a pilot plant that will use their electrolyzer technology to turn CO₂ emissions into useful chemical products like ethylene.
Dioxycle has raised a total of $17M in funding over 2 rounds:
Their latest funding was raised on Jul 26, 2023 from a Series A round.
Dioxycle is funded by 4 investors, including
- Breakthrough Energy Ventures
- Lowercarbon Capital
- Gigascale Capital
- Carbon to Value Initiative (C2V Initiative)
Sarah Lamaison is CEO.