Hydrogen and oxygen used as fuel in internal combution engine

[shivakumar06]

why cannot hydrogen and oxygen not used in internal combution engine as fuel? it would be pollution free.

 

[Mech_Engineer]

It can be, but you have to get the hydrogen from somewhere, typically through chemical separation processes such as electrolysis. So Hydrogen is not available to be mined or drilled, it must be made (separated) using energy. Where that energy comes from is another problem.

Additionally, hydrogen has a much lower specific energy density than hydrocarbon fuels, and it's difficult to store in large amounts compared to gasoline or diesel because it requires high pressures and/or low temperatures to get the density up. Metals used in engines today also have problems with hydrogen embrittlement which reduce their strength and wear properties.

These are just a few of the problems.

 

[Enthalpy]

One idea behind hydrogen is that it can be consumed in a fuel cell, whose efficiency is better than a thermal engine. So engineers and companies don't invest time in piston engines for hydrogen and go directly to fuel cells.

 

[pukb]

energy density of hydrogen is much greater than that of gasolene but only when it is compressed to a high pressure which requires external energy. and reasons mentioned by Mech Engineer.
Materials which can take up such high thermal stresses does not exists because metals suffer with hydrogen embrittlement at high temperatures and non metals like ceramic and plastic are not tough enough and melt respectively.
With advanced materials used in turbine blades with efficient cooling, such engines can be made.