Hydrogen peroxide can be used in many ways: you can bleach your hair, disinfect your mouth and treat wounds. It kills bacteria and inhibits the growth of molds and yeasts. But smearing it on your iPhone is not a good idea. In a recently updated support article, Apple warns that hydrogen peroxide should not be used to disinfect your iPhone, iPad, Mac, Apple Watch, HomePod, AirPods, and the like. It is allowed to use products with 75% ethyl alcohol, for example wet alcohol wipes.
Apple writes:
Can I use a disinfectant on my Apple product ?
You may wipe the hard, non-porous surfaces of your Apple product, such as the display, keyboard, and other exterior surfaces, with a 70% isopropyl alcohol wipe, a 75% ethyl alcohol wipe, or a Clorox disinfectant wipe. Do not use products containing bleach or hydrogen peroxide. Do not allow moisture to enter the openings and do not immerse your Apple product in cleaning agents. Do not use disinfectant on textiles or leather surfaces.
It is therefore better not to use bleaching agents and you should be careful that no moisture enters through openings when you are cleaning. Soaking is also not a good idea, also because moisture damage is not covered by the iPhone warranty or the warranty of your other products.
You can read everything about cleaning your iPhone in our separate tip.