A much more useful ocean-going consumer of solar power would instead produce ammonia, and release it into ocean currents flowing away from land. Releasing iron oxide dust along with it would amplify its useful effect.
The useful effect would be hundreds or thousands of square miles of additional photosynthesis downstream pulling carbon from the air.
If the unit were also to concentrate CO2 and release it dissolved into the water along with the ammonia, that might speed uptake. The waste oxygen produced along with the ammonia would also be useful dissolved into the current.
Micro-organisms scattered throughout the biosphere are astonishingly efficient at taking up dilute ammonia, and accelerating growth of everything around them.
Ammonia production is the best-fit energy sink for rural wind turbines far from an electric grid. The ammonia is immediately useful to farmers, on the spot, as fertilizer, fuel, and cash crop. Intermittent power causes no difficulty; produce when there's wind, wait when there's not. Kelp farmers would find wind-powered ammonia production equally useful. Unlike solar panels, wind turbines do not block sunlight.
Were somebody to do that, that somebody would assuredly be waiting for that year's Nobel.
For small-scale production, practicalities of providing chemically pure nitrogen and hydrogen may be gating factors, rather than actual synthesis.
Just any electrochemical synthesis process is very inefficient, that's thermodynamics and you can't do anything about that
The most dumb and simple electrochemical fuel production process — electrochemical production of ammonia, is nowhere close to commercialisation despite chemical industry trying to do that for more than a century