It is a total bull. Go ahead with it only, if you believe perpertum mobile can be built.
The situation is as simple as this: you have to first produce the fuel mixture by breaking water into oxygen and hydrogen. This requires energy. In ideal world, it would be the same amount of energy this mixture will produce while turning back into water (burning). Even then, you would just have a device that will indefinitely keep breaking water up and then producing it again - not a single bit of energy left to run anything else. Gets worse. The technical world is not ideal and there is no device with a 100% efficiency. There are always losses on the way. For that reason any gizmo like this has to end up in minus whatver you do. Tell your fried to wake up .

 

^^^^^ this

Previous post about vacuum gauge