Oxide-derived copper nanocrystal catalyst.
According to Matthew Kanan, an Assistant Professor at Stanford, “The catalyst on the electrode surface consists of a novel copper-based material. When there is an applied potential, carbon monoxide is reduced into ethanol and other products including acetate, and propanol.” The process can be operated at room temperature and atmospheric pressure.
Typically, ethanol is produced using a fermentation reaction. Here, corn or other sugar sources are produced into methanol using micro-organisms. However, this process means that a vast amount of land and water is needed to grow the crops. Additionally, the ethanol production to water use ratio can be in the range of 3:800 in some areas of the US. Needless to say, using the term ‘green’ to describe fermented ethanol has been the subject of heavy debate.
As Kanan points out, though, his solution doesn’t use fermentation, it “demonstrates the feasibility of making ethanol by electrocatalysis.” But he does admit “we have a lot more work to do to make a device that is practical."
Kanan explains, “Any conventional anode can be used for the water oxidation: steel, nickel, platinum. Our experiment is designed to focus on the cathode. We use a 3 electrode set up, cathode, reference electrode, to measure the potential of the cathode, and the anode. If you were to make an actual device you would have only 2 electrodes and then optimize the transfer of the electrolyte and electrons between the anode/cathode.”
The cathode is produced from copper oxide. Instead of a typical copper catalyst, which has nanoparticles lying on top of each other, this catalyst is formed from nanocrystals. These crystals are interconnected into a continuous network with well-defined grain boundaries. This catalyst appears to be over 10 times more efficient than traditional copper catalysts in the conversion, as 57% of the applied electricity goes into the target reaction.“The potential at the cathode compared to the theoretical minimum is about half a volt away,” said Kanan. “To determine the power needed for the reaction you need the over potential of the anode. Therefore, we don’t have a full cell yet to see a power draw. However, assuming normal performance for the anode and a good ion conductor in-between, I think it is reasonable to have something that operates at 2 volts.”
To increase the carbon neutrality of the system, renewable energies and CO from a non-petroleum source must be used. Using CO2 from the atmosphere to produce CO would certainly introduce a closed-loop system.
“What we think is important and exciting about this work is the possibility to make liquid fuel using primary renewable energy to drive the synthesis. We don’t have an efficient way to make liquid fuel from renewable energy, but this is a step in the right direction. There is, however, high and low temperature progresses to convert CO2 into CO very efficiently. This catalyst can help to make the next step to convert that CO into a liquid fuel,” assured Kanan.
With innovative energy solutions such as Kanan’s perhaps society can keep the power running and avoid any sort of Mad Max-esque future.
Source Matthew Kanan, an Assistant Professor at Stanford, and Stanford University