Why is water considered ionic in fuel cells but otherwise covalent?

If water, $\ce{H2O}$ is a covalent compound formed by sharing of electrons, why is it said (in case of fuel cells) that formation of water from hydrogen and oxygen is a redox reaction (transfer of electrons, not sharing). This would make it an ionic compound.

Any insights? Note that, the concept of water being formed as a result of redox reaction is highlighted in fuel cells (which is the basic principle of fuel cells - generating electricity by exploiting this transfer of electrons).

I know how fuel cells work, and it is indeed a redox reaction; but my doubt is - can water be formed by both covalent/ ionic means? (In textbooks, or in exams when asked to identify bonding present in water); when both covalent and ionic type can be achieved in its formation? Is both "covalent" and "ionic" correct while describing the formation of $\ce{H2O}$ molecule?

• Why can't you have covalent compound formed via redox reaction ? – Babounet Feb 7 '15 at 16:29
• Perhapse it is referring to the polar nature? (vs organic solvents which are nonpolar) – Dale Nov 11 '15 at 18:25

Water is certainly a covalent compound. Being produced from electron transfer doesn't mean that it is ionic. In a fuel cell, hydrogen is first ionized: $\ce{H2 <=> 2 H+ + 2 e- }$
Next, the electron moves to the other electrode, reducing oxygen while doing electric work: $\ce{O2 + 4e- -> 2O^2^-}$
Finally, hydrogen ions and oxide ions unite to form water: $\ce{2H+ + O^2^- -> H2O}$
Note, however, that water can self-ionize and become ionic, although these ions have only a low concentration of $10^{-7} M$ in pure water under room conditions. The presence of solutes and temperature of water affects the amount of water ionized at any given moment.