If we could burn water our world would be a paradise, in which we would have resolved every energy need because water is an unlimited source and its hypothetical combustion would be clean in an y case. Instead, the reality is totally different. The simple explanation is that water is not a fuel, as we well know and it can't have an useful reaction with any other substance, to produce energy.

The only reaction of H2O somewhat similar to a combustion is its spontaneous oxidation performed by gaseous fluorine (F2), the only substance able to oxidize O in water to produce the corrosive gaseous HF (hydrofluoric acid) and O2 (the oxidation product):

2 F2 + 2 H2O ====> 4 HF + O2 (1)

In this reaction, F2 plays the same role of O2 in the classic combustions but, very sincerely, I wouldn't recommend this reaction for an engine to my worst enemy because of the extremely corrosive and reactive substances involved.

The only alternative solution to the impossible water combustion is to obtain from water a substance we can burn to obtain energy and this substance is hydrogen (H2); for this purpose, we must spend energy to dissociate H2O by electrolysis using the charge of a set of batteries on the car.

The products of this dissociation are H2 (the true fuel) and O2, the combusting agent; these two gases can react in the engine, moving the and producing heat like the other fuels, but the products of this is again water, by this reaction:

2 H2 + O2 ====> 2 H2O (2)

The problem is just that the batteries, sooner or later, go out of charge and they must be recharged to recover their electromotive force and give the electric charge necessary to decompose water. The electric cars based on this working scheme are already a reality and they circulate in our towns, although in little number. Their main drawback is still that their batteries still haven't a long autonomy like the fuel engines, burning gasoline, methane and propane gas, alcohol or gas-oil.

A possible solution would be covering most of the exterior of the car with a coating made of the new organic polymers that will soon replace the photovoltaic cells made of silicon layers or wafers, alternatively doped p and n to create a potential difference and, consequently, the circulation of electric power.With this coating, the car and whatever vehicle could easily recharge its battery under the sunlight. In any case, water can be a product of combustion, never a reagent in it (apart from the reaction with F2).

Another solution is always to consume H2 stored in the car in the fuel-cells engine, in which O2 and H2 combine electrolitically with the reduction of the first (receiving electrons) at a cathode and the oxidation of the second (providing electrons) at an anode to produce H2O within a porous solid membrane between the electrodes and a catalyst made of platinum or platinum/ruthenium, covering the electrodes, once again with the reaction (2). The electrons so produced make work an electric engine that moves the car. The great, still unresolved problem is H2 storage inside a car, insufficient or too dangerous. Also in this case, H2O is only a combustion product, not stored in the car tank as a fuel.

The alternative scheme, the most used and encouraging, is to use the electric power of the batteries to make work directly an electric engine, without using H2O or H2 and its decomposition products and the yield is higher.

Learn more about this author, Aldo Bonincontro.
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