There was a company about 10 years ago in Canada that had a patent for hydrogen production. The company was called oxgen and I was on their mail list. They claimed to be able to produce two types of hydrogen one lower grade for heating and one higher grade for cars. The lower grade used coils submerged in water. Their patent was based upon a 13.5 volts @ 19 hertz square wave @ .5 amps. for the running of their demonstration engine. Then a natural gas company in Canada purchased a large amount of stock in the company. For about a year I received news E-letters on the progress of the company then one day no more website, no more E-letters. I built a 555 timer circuit at 19 hertz DC square wave at 1.5 amps and current limited with a resistor. It did not seem to peter out like straight DC electrolysis does requiring more current for the same work. But I did not do any major large experiments or use multi plate electrodes.