Longer.
This is because that each bond should be a single bond rather than a double bond. If Oxygen were to double bond with itself and hold a bond with Hydrogen, then Oxygen would have too many valence electrons to hold.
It would also be longer due to the fact the double and triple bonds are shorter due to it needing to be closer together.
When mapping out the bonding for H2O2, keep in mind that Hydrogen is an element that tends to stray to the side as it likes to be a loner. Carbon is the element that would typically take the center and Oxygen would usually double bond with itself.
Therefore, the single bond in oxygen in H2O2 would be longer due to the fact that it would be a single bond rather than double or triple.
Hope this helps!
