If my understanding is correct, the goal is to reduce aviation effect on climate change.
There is an ongoing project [1] by US NAVY to turn seawater into jet fuel. This way we would not need to burn fossil fuels and would not need to throw away much of existing aviation technology.
Water is free [1], Carbon Dioxide is free [2]. Energy is never free.
You need some big solar panels or a nuclear reactor to get the energy. (Can you put a wind turbine in a ship?) (The usual trick of burning fuel to produce energy is not a good idea here.) So this kind of process should not be interpreted as "water -> fuel" but like "energy -> fuel".
It can be useful to store energy for a while, or producing fuel using a nuclear reactor in the carrier and using the fuel in the planes. (I'm not sure that this is economical or tactically a good idea.)
If the idea is to produce the fuel on land, it is much more efficient to sell the energy and buy fuel. The energy you sell will cause a electric plant that use carbon to close and the net effect will be bigger reduction of the CO2 level.
From the article:
> Laboratory team led by Heather Willauer announced it had used a catalytic converter to extract carbon dioxide and hydrogen from seawater and then converted the gases into liquid hydrocarbons at a 92 percent efficiency rate.
I really doubt this. Organic reactions have a horrible low efficiency, specially the ones that create complex molecules using simple ones. (Perhaps the 92% efficiency is counting how many of the CO2 are converted, but the most important part of this reaction is the energy. If it convert the 92% of the CO2, but it stores only the 1% of the energy, it is very wasteful.)
[1] Processing water to avoid the problems with salt and tartar may be a big problem, so it may not be so easy.
[2] But the concentration is usually low, that is generally bad for fast and efficient reactions.
In terms of energy, it's not a contest and it's not a hangup. Carriers are already powered by nuclear reactors. They have about 1500MW of steam power available as a matter of course. Compare to 25MW if you paved the flight surfaces with solar panels and parked it at the equator on a sunny day with perfectly calm seas and measured at noon. Unlike solar in this example, the nuclear design is not bumping up against physical constraints and could be scaled up quite dramatically if there was a compelling reason to do so. Fuel production would be a compelling reason.
The chemistry and chemical engineering problems you point out are the major hangups.
Sayong they are converting water to fuel focuses on the wrong (least important) part of it. The point is that it fixes CO2 from the air into hydrocarbon fuels via generating carbon monoxide and using the Fisher troph process to assemble fuel molecules. This is really just congealing electrical energy into hydrocarbon fuel. For now in the lab, you still get that energy from fossil fuels. Presumably in the future you would use this process to congeal extra solar or wind energy into fuel rather than keep them stored in batteries
In this particular case, they are planning to take energy from carrier's nuclear power plant.
More generally, either hydrogen or fuel synthesis requires energy to come from somewhere; In this regard it is no different than re-building airplanes to use hydrogen, as the original article suggests.
The point is that we might have better chances synthesising fuels usable in existing planes, versus re-building majority of aviation to use hydrogen.
There is an ongoing project [1] by US NAVY to turn seawater into jet fuel. This way we would not need to burn fossil fuels and would not need to throw away much of existing aviation technology.
[1] https://www.eurekalert.org/pub_releases/2020-07/uor-lch07152...