So I watched the video on the EBH2 website as I had similar questions and wondered if it wasn't lost translation somewhere. The number of spelling mistakes in the video not withstanding, I think I know what they should have said.
They mentioned again in that video "with 2 litres of water you can product up to 1MW per week". If you break that down to kWh at 168 hours per week, you get 5.95 kWh. Allowing for efficiency loss on the separation and power generation sides, 5.95kWh from 6.6kWh is believable. So it's 2L of water a day, not 2 litres of water.
What I'm still not understanding is how they are splitting the hydrogen with a net positive energy output. This isn't physically possible without some sort of external energy input.
Electrolysis of water: 2 H2O + energy > 2 H2 + O2
Burning of hydrogen: 2 H2 + O2 > 2 H2O + energy.
This is a net zero equation assuming 0 losses. That leaves 0 energy that can be removed and maintain the reaction. And that's only possibly in theory.
So where's the additional energy coming from? If it's a secret sauce catalyst then they should acknowledge that, because otherwise this is junk science.