Oak Ridge National Laboratories have come up with a catalyst that directly converts CO2 to ethanol. This may be a nice way to use excess renewable power, and may prove more useful than other energy storage methods (referring to the recent idea of storing such energy in hot rocks with around 25% round-trip efficiency). Read the Science Alert article here. OK, it was intended to actually produce some precursors as the first part of the conversion, and that ethanol was actually made in one step seems to have come as a bit of a surprise, but that is one of the interesting things about real science in that theory isn’t always borne out by experiment.
Quote from the ScienceAlert article:
Rondinone and his colleagues had put together a catalyst using carbon, copper, and nitrogen, by embedding copper nanoparticles into nitrogen-laced carbon spikes measuring just 50-80 nanometres tall. (1 nanometre = one-millionth of a millimetre.)
When they applied an electric current of just 1.2 volts, the catalyst converted a solution of CO2 dissolved in water into ethanol, with a yield of 63 percent.
This result was surprising for a couple of reasons: firstly, because it’s effectively reversing the combustion process using a very modest amount of electricity, and secondly, it was able to do this while achieving a relatively high yield of ethanol – they were expecting to end up with the significantly less desirable chemical, methanol.
At the moment there doesn’t seem to be data of how efficiently this converts electrical energy into chemical energy (so the ethanol can be later burned as fuel) and this research is only at the start, but nevertheless it does look promising as a way of reversing combustion. Of course, if that fuel was later used to drive a combustion engine and to generate electricity again, the round-trip efficiency would be pretty low overall, but if it’s heat you want (or simply to drive a car) then it could be cost-effective.