he hasn’t tried it! he just stated it couldn’t work ...he doesn’t know he believes it won’t work!
The second law of thermodynamics isn't on the cutting edge of physics. It's bedrock. It may, on some scale of time and distance be totally wrong, there are no known creditable, repeatable observations that refute it.
As a matter of law, the U.S. patent office cannot accept an application for a perpetual motion machine. The patent office was spending millions of dollars a year rejecting such applications. It is tedious and expensive to "disprove" these claims in legal sense.
People have been trying since time immemorial to find a perpetual motion machine and failing.
Engineering anyone? Hydrogen is the lowest energy fuel on the planet. Every other combustible produces more energy, even marshmelows.