A hydrogen/bromine reduction-oxidation flow battery system includes a bromine electrode, a hydrogen electrode, a membrane, a first catalyst, and a second catalyst. The membrane is positioned between the bromine electrode and the hydrogen electrode. The first catalyst is associated with the bromine electrode. The second catalyst is associated with the hydrogen electrode and at least partially formed from a subsurface alloy configured (i) to promote facile dissociation of H2, and (ii) to prevent bromide from adsorbing onto the hydrogen electrode.