Now do the math on how much electrical energy you used to free the hydrogen.

This is simply an HHO generator. It requires more energy to crack the water than you get back out. The result is a slight reduction in energy than you get back out. Really all this does is transform your energy source from electricity into a combustible gas. Industry has used this for ages for cutting torches.

A lot of people completely misrepresent what this technology is or does. It's not magic. It's not some hidden, secret technology. It won't make your car magically travel further. This technology is old, well understood, and for the bulk of people, is best ignored.

This is a demonstration of electrolysis. The reaction produces hydrogen and oxygen which makes a potent gas mixture which its production rate is dependent on the flowing current and surface area of the anode and cathode.

Now the thing to balance it against thermodynamics, is the battery which is also using electrolysis to make for an electrical current to make this reaction. The missing step is to making a feed back to keep the reaction going without the aid of the battery. Otherwise, you are just using the battery alone with extra steps and more waste. That gas explosion has to be utilized to drive an alternator to maintain the current. You could drive with permeant magnet motors to use the excess directly from the alternator and capture energy from the reverse emf to maintain the reaction or drive a crankshaft with the gas. As in many other demonstrations, the energy left over in ideal conditions is still very little. It will run into the same stumble as EVs.

On top of the previous excellent answers. Several companies are also working on hydrogen fuel cells for cars and other uses. There's several technical issues to overcome, one of which is the high degree of flammability and containment is difficult because the atoms are so small and 'slippery'.