Is it profitable to use water electrolysis to produce hydrogen as a fuel?

It's certainly not profitable. If you can make it profitable, you will be the greatest scientist of the 21st century! The electrical energy consumed in the water ionization process now belongs to secondary energy. In our opinion, this is a bit of a waste of energy. Under normal circumstances, the heat released when one mole (two grams) of hydrogen is burned is about 286 KJ, and the heat released when burned per kilogram of gasoline is about 46,000 KJ. The density of gasoline is 0.72 to 0.74 g/ml, and the average value is calculated to be 0.73. Then, burning a liter of gasoline releases heat of 0.73*46,000 = 33,580 KJ. The amount of hydrogen required is calculated to be 33,580/286 = 117.4 mol. The mol to volume conversion is 117.4*22.4=2629.76 liters, which is approximately 2.6 cubic meters. Therefore, the complete combustion of a liter of gasoline produces the heat bornnecessary to completely burn 2.6 cubic meters of hydrogen to achieve the same effect. So no matter how you look at it, it's very cost effective and inconvenient to use!