That's how I understand it as well. It harvest the brownian motion of atoms in graphene.
I definitely don't know enough about this subject to judge the plausibility of the claim but "graphene" and "limitless power" in the same headline does trigger a few red flags.
I can't find the actual electrical power generated by the prototype circuit in the press releases, but it sounds like in the mA power range? It is "limitless" as long as the graphene mechanically survives (wonder how long that buckling will take to compromise the graphene) and there is some kind of minimum temperature maintained for the given required amount of electrical power output desired. Definitely not "free energy", but always good to reach further down into the physical realm in Feynman's "Plenty of Room at the Bottom" sense.
I'm rooting around for alternative sources of the paper without success, but for those who have read it, what kind of graphene did they use (monolayer, CVD, GO, rGO, etc.)? I suspect that will somewhat throttle the manufacturing supply chain.
Batteries are the least interesting application to me. This brings "sensor dust" out of solid fantasy into the realm of possibility in the far future; at first it will be "sensor clods", but let it follow the same evolutionary Shockley-to-ARM development path, and let's see where it goes. Permanently implanted medical chips to measure the blood, nervous and other internal medicine metrics we want to get our hands on might be more miniaturized; need to figure out how to extract out the incredibly weak signal.
But that means the graphene sheet need to be hotter than the surroundings? Or is this just converting heat from the air and infrared radiation into electric energy?
I definitely don't know enough about this subject to judge the plausibility of the claim but "graphene" and "limitless power" in the same headline does trigger a few red flags.