The oxygen reduction reaction on Pt(111) and Pt(100) surfaces substituted by subsurface Cu: a theoretical perspective

The mechanisms of the oxygen reduction reaction (ORR) on Pt/Cu(111) and Pt/Cu(100) have been investigated by using density functional theory. Compared with pure Pt(111) and Pt(100), the adsorptions of ORR intermediates are weakened on both Pt/Cu(111) and Pt/Cu(100) surfaces. The ORR follows the oxygen dissociation mechanism on Pt/Cu(100) which is the same as that on pure Pt(100). However, the ORR mechanism is the peroxyl dissociation mechanism on pure Pt(111), hydrogen peroxide dissociation on Pt/Cu(111). The rate determining step is OH + H+ + e(-) -> H2O on Pt/Cu(100) and pure Pt(100), O + H+ + e(-) -> OH on pure Pt (111) and OOH + H+ + e(-) -> H2O2 on Pt/Cu(111). Compared with the energy barrier of the rate determining step on pure Pt(111) (0.86 eV) and Pt(100) (0.76 eV), the ORR reaction activity is improved on Pt/Cu(111) and hindered on Pt/Cu(100), with the barriers of 0.40 and 0.85 eV, respectively. For the effects of electric potential, OH protonation is favorable thermodynamically at a broad electrode potential (from 0 to 1.23 V) on the Pt/Cu(111) surface, in agreement with the high durability of Pt/Cu observed in experiments. The working potentials of Pt/Cu(111) and Pt/Cu(100) are predicted to be 0.39 and 0.73 V, respectively.