Protonic heterojunction in intermetallide-potassium hydroxide dihydrate-graphite heterostructure

New original heterostructures that incorporate graphite and iron titanium (TiFe) intermetallide as materials of two electrodes and KOH·2H 2 O as a solid electrolyte ( T melt = 315 K) are described. For room-temperature activated cells, the emf amounts to ∼1.4–1.1 V at 263–310 K, where the contribution of the TiFeH x /KOH · 2H 2 O heteroboundary accounts for 0.9–0.7 V. The replacement of protium by deuterium leads to a ∼100 mV change in the potential of this heteroboundary, which is evidence for a potential-determining role of protons. The isotope exchange confirms the kinetic reversibility of the proton transition via the TiFeH x /KOH · 2H 2 O heteroboundary, which is also indicative of the formation of a protonic heterojunction.