TIFR researchers have developed a magnesium-based method to rapidly convert CO₂ and water into fuel and hydrogen, potentially usable on both Earth and Mars.
Excessive CO2 emissions are a major cause of climate change, and hence reducing the CO2 levels in the Earth’s atmosphere is key to limit adverse environmental effects. Rather than just capture and store CO2, it would be desirable to use it as carbon feedstock for fuel production to achieve the target of “net-zero-emissions energy systems.” The capture and conversion of CO2 (from fuel gas or directly from the air) to methane and methanol simply using water as a hydrogen source under ambient conditions would provide an optimal solution to reduce excessive CO2 levels and would be highly sustainable.
Researchers at Tata Institute of Fundamental Research (TIFR), Mumbai, demonstrated the use of Magnesium (nanoparticles and bulk) to directly react CO2 with water at room temperature and atmospheric pressure, forming methane, methanol, and formic acid without requiring external energy sources. Magnesium is the eighth most abundant element in the Earth’s crust and the fourth most common element in the Earth (after iron, oxygen, and silicon).
Fast, Room-Temperature CO₂-to-Fuel Process
The conversion of CO2 (pure, as well as directly from the air) took place within a few minutes at 300 K and 1 bar. A unique cooperative action of Mg, basic magnesium carbonate, CO2, and water enabled this CO2 transformation. If any of the four components were missing, no CO2 conversion took place. The reaction intermediates and the reaction pathway were identified by 13CO2 isotopic labeling, powder X-ray diffraction (PXRD), nuclear magnetic resonance (NMR) and in-situ attenuated total reflectance-Fourier transform Infrared spectroscopy (ATR-FTIR), and rationalized by density-functional theory (DFT) calculations. During CO2 conversion, Mg was converted to magnesium hydroxide and carbonate, which may be regenerated.
Mg is one of the metals with the lowest energy demand for production and generates the lowest amount of CO2 during production. Using this protocol, 1 kg of magnesium via simple reaction with water and CO2 produces 2.43 liters of methane, 940 liters of hydrogen and 3.85 kg of basic magnesium carbonate (used in green cement, pharma industry, etc.), and also small amounts of methanol, and formic acid.
In the absence of CO2, Mg does not react efficiently with water, and hydrogen yield was extremely low, 100 μmol g-1 as compared to 42000 μmol g-1 in the presence of CO2. This was due to the poor solubility of magnesium hydroxide formed by the reaction of Mg with water, restricting the internal Mg surface from reacting further with water. However, in the presence of CO2, magnesium hydroxide gets converted to carbonates and basic carbonates, which are more soluble in water than magnesium hydroxide and get peeled off from Mg, exposing fresh Mg surface to react with water. Thus, this protocol can even be used for hydrogen production (940 liter per kg of Mg), which is nearly 420 times more than hydrogen produced by the reaction of Mg with water alone (2.24 liter per kg of Mg).
Simple, Safe, and Sustainable Process
Notably, this entire production happens in just 15 minutes, at room temperature and atmospheric pressure, in an exceptionally simple and safe protocol. Unlike other metal powders, the Mg powder is extremely stable (due to the presence of a thin MgO passivation surface layer) and can be handled in the air without any loss in activity. The use of fossil fuels needs to be restricted (if not avoided), to combat climate change. This Mg protocol will then be one of the sustainable CO2 conversion protocols, for a CO2-neutral process to produce various chemicals and fuels (methane, methanol, formic acid, and hydrogen).
Planet Mars’ environment has 95.32% of CO2, while its surface has water in the form of ice. Recently, the presence of magnesium on Mars in abundant amounts was also reported. Therefore, to explore the possibility of the use of this Mg-assisted CO2 conversion process on Mars, researchers carried out this Mg-assisted CO2 conversion at a lower temperature. Notably, methane, methanol, formic acid, and hydrogen were produced in a reasonable amount. These results indicate the potential of this Mg process to be used in the Mars’ environment, a step towards magnesium utilization on Mars, although more detailed studies are needed.
Reference: “Direct CO2 capture and conversion to fuels on magnesium nanoparticles under ambient conditions simply using water” by Sushma A. Rawool, Rajesh Belgamwar, Rajkumar Jana, Ayan Maity, Ankit Bhumla, Nevzat Yigit, Ayan Datta, Günther Rupprechter and Vivek Polshettiwar, 31 March 2021, Chemical Science.
DOI: 10.1039/D1SC01113H
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2 Comments
… there are so many alternatives out there, but we pick a end game scenario.
Who said that humans are intelligent creatures after all…
“Excessive CO2 emissions are a major cause of climate change, and hence reducing the CO2 levels in the Earth’s atmosphere is key to limit adverse environmental effects.”
That claim is commonly made, but it relies primarily on Global Circulation models that run too warm, and have contradictory predictions of precipitation at regional levels. That is, the models and any conclusions are problematic.
“The capture and conversion of CO2 (from fuel gas or directly from the air) to methane and methanol simply using water as a hydrogen source under ambient conditions would provide an optimal solution to reduce excessive CO2 levels and would be highly sustainable.”
This is an assertion made without citation or logical support. Done on the scale to undo what humans are doing would almost certainly reduce the relative humidity at, and downwind from, the plants doing the CO2 and H2O capture. This would result in less rain downwind. Surface and groundwater is already a precious commodity that is being extracted from aquifers at rates exceeding the recharge rate, and consequently resulting in land subsidence. Relying on groundwater would exacerbate the situation and impact food production.
“Magnesium is the eighth most abundant element in the Earth’s crust and fourth most common element in the Earth (after iron, oxygen, and silicon).”
Extracting and refining magnesium is an energy intensive process. While Mg may be relatively plentiful in crustal rocks, it is invariably tightly bound to silicon and oxygen, or carbon and oxygen. Therefore, one needs an abundant and cheap source of electricity, which probably only thermonuclear fusion can provide. We have not yet solved the problem of commercial fusion. When we do, I expect ‘Green’ opposition to making the transition.
I would expect that a commercial plant producing methane and methanol from magnesium will be more challenging than demonstrating the conversion in a laboratory. God forbid that the plant should experience a magnesium fire, because it is almost impossible to extinguish with water, CO2, or even sand.