The structure is on approximately the same scale as the wavelength of visible light. I think that's in common with other recent ultra-black materials, it's either that there's just a huge amount of surface area or some sort of quantum-mechanics effect.

Aerogels can have a surface area of ~2,500 m2 g-1, which is incredibly high.

I wonder if this material, being made of carbon and likely having a similarly high surface area, would make a good capacitor.

https://en.wikipedia.org/wiki/Aerographite#Potential_applica... claims 1.25Wh/kg. I hope that isn't for the lightest variant; in Wh/m^3, that wouldn't be that good.

If the structure would be greater it probably would be transparent.