It's well known that if you mix $\ce{H2}$ and $\ce{O2}$ in ambient conditions, the $\ce{H2}$ will be stable indefinitely, and will only react with $\ce{O2}$ to form water when ignited by a flame. The reason being that for the reaction
$$\ce{2H2 + O2 -> 2H2O} \label{rxn:1}\tag{1}$$
to occur, first the bonds must be broken in $\ce{H2}$ and in $\ce{O2},$ which is an insurmountable activation energy at room temperature.
So I am confused why a hydrogen fuel cell works at room temperature without ignition, as it is powered by the same chemical reaction \eqref{rxn:1}.
In particular, why can the strong double bond in $\ce{O2}$ suddenly be broken in this context without a flame?
My best guess is that somehow the electron sea in the copper wire acts as a catalyst. If this is true, what are the details of this mechanism that allows the $\ce{O2}$ bond to break at room temperature?