Advantages/disadvantages
Energy transfers involved (mechanical, chemical, kinetic, nuclear)
How sustainable is it?
A fuel cell is a battery but unlike a battery where the chemicals that react and the reactants are stored in the cell, the chemicals are provided from outside the cell and the reactants removed. With a hydrogen fuel cell, the chemicals are hydrogen and oxygen reacting through a membrane to form water which is vented. Ideally the oxygen could be obtained from the atmosphere but most hydrogen fuel cells require pure hydrogen and oxygen. Obviously more chemicals can be stored externally than would be possible to store in a battery and as the reactant is removed, you're not carrying dead weight around. Unfortunately, hydrogen has a low volumetric energy density, when compressed at commercial pressures ( 150 bar which is 2,100 psi ), it takes twenty times the volume of gasoline to hold the same amount of energy and as most hydrogen fuel cells require pure oxygen, oxygen needs to be carried as well. There are now methanol fuel cells which use methanol and air for the reaction. Another downside is that hydrogen is commercially produced by the gasification and steam reformation of natural gas so it is produced from fossil reserves. It can be produced by the electrolysis of water but it takes more energy to electrolyse the water then you get from reacting the chemicals. The energy transfer is chemical to electrical. It is not sustainable but can be an effective mean of temporarily storing energy from other sources chemically. The natural gas from which it's normally produced from is chemically stored solar energy collected by photosynthesis millions of years ago.
Hydrogen fuel cells are electrochemical cell which used to converts chemical energy into electricity. It can be made from natural gas or it can be made by passing electric current through water. The advantage of hydrogen is it not produces carbon dioxide when burning. That is, hydrogen is less pollutant in the air. The sources to produce hydrogen are solar (photovoltaic cells), wind, and nuclear hydrogen etc.
They burn hydrogen to make electricity.
The hydrogen can come from any source. The main sources that I know of are biofuels, or electrolysis of water (for example, as a storage medium for surplus solar or wind energy)
The advantages: it can be made from water, anywhere that you have water; it can be stored indefinitely with minimal losses
the disadvantages: it's a bit dangerous to handle, it is a gas (and potentially leaks easily, though leaks aren't a safety hazard in a properly designed system
The other questions make me suspect you're lazywebbing your homework, so I'll leave off here.
The hydrogen fuel cell operates similar to a battery. It has two electrodes, an anode and a cathode, separated by a membrane. Oxygen passes over one electrode and hydrogen over the other.
The hydrogen reacts to a catalyst on the electrode anode that converts the hydrogen gas into negatively charged electrons (e-) and positively charged ions (H+).
The electrons flow out of the cell to be used as electrical energy. The hydrogen ions move through the electrolyte membrane to the cathode electrode where they combine with oxygen and the electrons to produce water. Unlike batteries, fuel cells never run out.
They use hydrogen and air to make electricity.
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Is their origin solar/ non-solar?
Advantages/disadvantages
Energy transfers involved (mechanical, chemical, kinetic, nuclear)
How sustainable is it?
