# Can an alloy catalyst change during a reaction?

I am studying the reaction pathway of oxygen evolution reaction (OER) on a PtNi alloy catalyst using density functional theory (DFT). What I found is that, for different intermediates, the most stable configuration of the PtNi(111) surface can be different. Let's say I have a $$2\times2$$ cell, and the most stable surface composition for the HO* intermediate is Pt$$_4$$, whereas for the O* intermediate, the most stable surface composition is Pt$$_3$$Ni (O* attached to Ni). My question is as follows:

Is the alloy catalyst allowed to change during the reaction? If we consider the reaction step HO* → O*, the easiest way is to assume the catalyst doesn't change during the reaction. However, if the energy barrier of the reaction is lowered so much when O* bonds Ni that it compensates the energy barrier of swapping a surface Pt atom with a subsurface Ni atom, does it suddenly become favorable? I think it comes down to comparing one large energy barrier vs. two small energy barriers, but I can't find any theories regarding this. Any suggestion is appreciated.

• I am not very familiar with the catalyst system you mention, but if the catalyst is changed by one step of the reaction, then won't the catalyst be deactivated eventually? Change of surface structure of catalysts is quite common, but if that deactivates the catalyst, there has to be a way to return to the original configuration. Aug 24 at 3:42