Well, to do as I believe you mean, you would take the electricity form solar cells, and then separate the hydrogen and oxygen through
electrolysis. Now you then need to capture this hydrogen gas for use. The hydrogen gas is the energy storage. Storing it requires a compressor and a high pressure tank, and can be dangerous. The fuel cell creates energy, by recombining the oxygen in the air with the hydrogen. For use in a house, you would also need an
inverter. This is all well and good in theory. However, there are several problems involved. The life of the fuel cell membrane for one. Maybe there is a good one developed since I looked into it, but there has no to my knowledge, none that is affordable and doesn't degrade with the impurities to be expected. Hydrogen doesn't compress easily or safely, outside of high costs.
Outside of this basic idea.... which is sound... it seems to me the best research you can do is to find out the efficiency of conversion to gas, and back to energy, and then the costs of containing the hydrogen storage. As an exercise, I think the costs and upkeep of the fuel cell itself is relevant also, but maybe your teacher doesn't.
Good luck.