Effect of Platinum Incorporation on the Energetics and Oxygen Chemisorption Properties of the Ni(1 1 1) Surface

The changes resulting from platinum substitution and PtNi surface alloy formation in the energetic, structural, and electronical properties of the Ni(1?1?1) surface and the following decrease in the strength of oxygen chemisorption are investigated by DFT computations. Platinum substitution decreases both the total energy and the tensile stress of the Ni(1?1?1) surface. The decrease in the surface stress leads to a decrease in the degree of electron transfer from the surface nickel atoms to oxygen adatoms and, as a consequence, to a weakened oxygen chemisorption stability on the surface. The overall results confirm that PtNi surface alloys have lower oxygen affinity and a larger tendency to stay in the metallic form compared to monometallic nickel, and this is one of the reasons of increased catalytic activity and enhanced stability of PtNi bimetallic catalysts in oxidative steam reforming, especially at low reaction temperatures.