I doubt any process we invent is ever going to be more efficient than just letting plants convert the sunlight into sugar and then letting yeast convert the sugars into ethanol.
Actually this process is already more efficient than photosynthesis to extracting sugar which yeast can only ferment C6 sugars and half a plants sugars are C5, sugar cane is one of the most efficient C4 plants in photosynthesis and it peaks out at 1% photonic conversion of light energy to all carbohydrates which 30% is lignin, and 70% is split 50/50 with C6+C5 sugars. So 1% of the sunlight falling on a sugar cane plant gets converted to carbohydrates and only 45% of that is fermentable into ethanol, yeast are about 60% eff at converting that 45% into ethanol the rest ends up as CO2 gas. for an overall sun to ethanol via yeast eff of 0.0027%
this electrochemical process is 63% faraday efficient meaning 63% of the electrons flowing into the catalyst end up creating molecules of ethanol. Modern solar cells are 18% efficiency for converting photons into electron current. given a 63% electron to ethanol conversion the overall eff is 11.35% that is a 2 full order of magnitudes more efficient put another way for a given sq meter of area in the sun this process would produce on an energy equivalent basis 42 times the ethanol than plants.
the simple truth is terrestrial plants are terribly inefficient at solar photosynthetic conversion. marine plants with out lignin production can hit upwards of 10% specifically kelp and other brown algae.
for those wondering I hold a masters in Geosciences with 2 full years of NSF funded research in biofuel efficiency. The numbers above are ruff but factually accurate in relative terms. I currently make a killing in the oil industry so I have no vested interest to pimp a technology. I’m just pointing out that electrochemical process almost always beat nature.
scale is the issue as is catalyst cost, this would be a great way to store wind energy at night when the costs go negative as in the power district pays large consumers to use enegry so the grid stays stable. it happens here in Texas a lot during the winter. ethanol is also one OH molecule from ethane the building block of nearly all petrochemicals, plastics HDPE,LDPE ect. ethene can be polymerized into any even number hydrocarbons, C8 is octane,C12 is dodecene aka jet fuel,C16 is diesel.the technology to dehydrate ethanol to ethane is industrial scale used every around the world, the fluid catalyst tech to convert ethane to ethene and to dimers,trimers and higher poly molecules is also industrial scaled.