Water dissociation on boron-doped single crystal Ni₃(Al, Ti) (110) surface

Previous work demonstrated that water dissociates into hydrogen on the Ni₃(Al, Ti) (100) surface. There is clear evidence that this dissociation reaction results in the reduced ductility of many polycrystalline aluminum-based alloys in a moist environment. Ductility measurements further showed that microalloying with boron markedly improves the ductility of these polycrystalline alloys. To explore the effect of boron, we first dosed the surface of clean Ni₃(Al, Ti) (110) with controlled amounts of boron, using a specially designed low-energy boron ion source, followed by low-temperature exposure to D₂O and temperature-programmed desorption. Results indicated that water dissociates into atomic hydrogen on clean Ni₃(Al, Ti) (110) boron-free surface, which was further verified by x-ray photoemission studies. This dissociation reaction is strongly suppressed by boron adsorption at a coverage of 0.25 monolayer. Auger studies on boron-modified surfaces showed that boron is oxidized in this process. These studies indicated that addition of boron suppresses water dissociation into atomic hydrogen. The significance of this observation will be discussed.