I have been investigating ORR in alkaline medium and our conclusion was a 2+2 electron transfer, that is, first oxygen is reduced to peroxide and then peroxide to hydroxide. How much the reaction looks like a 4e- process depends on the performance of your electrocatalyst to reduce peroxide to hydroxide.

I guess in acid medium this phenomenon must be similar, since ORR on Pt is reported to produce a little amount of H2O2. However, it is true that H2O2 reduction to water on Pt in acid medium must be a very favourable reaction as we practically observe a 4e- process. If graphene only shows a 2e- transfer process is because just catalyses the reaction of oxygen to peroxide, the same that happens in alkaline medium. This is the reason to use a carbon+electrocatalyst system in alkaline medium, i.e. the carbon carries out the reduction of oxygen to peroxide and the electrocatalyst the reduction of peroxide to hydroxide.

Yes you are right to the extent that the 2e- or 4e- transfer mechanism depends on whether the catalayst produces peroxide (H2O2 or HO2-) or hydroxide (H2O or OH-). But i want to know how Pt (and some noble metals like Pd, Au) helps 4e- ORR while almost all the other elements are not able to follow 4e- pathway in acid, however they may/may not follow 4e- ORR in alkali.

If somebody helps me to understand which sort of bond does Pt make with the adsorbed oxygen to give the 4e- pathway then it would be great to search some other elements that may form the similar bond with oxygen. Or if someone can provide me some other metals/non-metals that follow 4e- ORR in acid then it would help me a lot.