> it roughly doubled the current density at the anode without requiring any additional voltage
Do I understand correctly that the magnet just makes the anode behave like a bigger anode, and does not make the process more energy-efficient?
Do I understand correctly that the magnet just makes the anode behave like a bigger anode, and does not make the process more energy-efficient?
This discovery maintains efficiency that would normally require a larger electrode surface. It doesn't double the chemical energy output from the electrical energy input. That would be impossible as conventional electrolyzers are already more than 50% efficient. It (potentially) improves the economic efficiency more than the thermodynamic efficiency.
In a perfectly efficient process all of the resistance would owe to H2O splitting, but we know that's not the case - about half the resistance energy was creating waste heat.
If its like an LEDs resistance which has a voltage drop component which produces light and a linear ohmic resistance which produces waste heat. This would be like getting twice the current (and light) across an LED from the same voltage.
Either the voltage drop has been reduced, or the ohmic resistance is reduced. Either way, we can lower the voltage and produce the same amount of light that was possible without the magnetic hack. Same current with less voltage is less power, for same amount of light or H2O split.
If you look at the full paper through sci-hub [1], it's an efficiency improvement specifically at higher current densities. In the left hand side of Figure 1, the magnetic/non-magnetic curves are indistinguishable at very low current densities. Those low current densities also have the lowest overvoltage and highest efficiency per gram of H2 produced. But for an industrially optimized device you want to push production rates higher for a given electrode area, which requires more current density, which also requires more voltage. Higher current density implies higher energy wastage since the voltage has to go up too.
The voltage increase with higher current density rises more slowly in the presence of a magnetic field. By the time current density reaches 50 mA/cm^-2, the setup with the magnetic field needs several millivolts less than the control setup without a magnetic field.
> "Online O2 detection also confirmed quantitative OER Faradaic efficiency with and without the presence of a magnetic field (Supplementary Fig. 17)."
But it looks to me like this effect is demonstrated as really significant already, for all the catalysts bar one. Application of it cant be far away. A bit like sticking a magnet on an engine block and getting loads more horsepower !
Typical motors used in electric cars are a lot more powerful and efficient than their internal combustion engine counterparts ;)
Meanwhile, if the build-cost gets low enough then it suddenly becomes worth installing electrolysers for those occasional times when the cost of electricity goes negative and all that matters is throughput.