FUEL CELL

In This process the battery works ,

Oxygen  pulls hydrogen to bond with it. Here the electronegative is Oxygen  because it has as compared to hydrogen is positive 

When this happens the charge hydrogen moves and generates the energy since the hydrogen is an energy carrier , but when a bond happens between two elements , During this journey only hydrogen moves and conducts the energy  .

The fuel cell in this takes the energy in this battery in two ways, one way is from electrons and the second way is to take from ions which protons form hydrogen. 

It consists of an oxygen and hydrogen atom held together by  a H2O 

In only water is form h2o which contain single bond of hydrogen and two oxygen 

In process the estimate energy is around 90 MJ to 120 MJ  of 1kg hydrogen