Extended Born-Haber cycle for explaining oxygen-chlorine chemisorption scaling on transition metals

We study a wide range of transition metals and characterize how they bind O and Cl. We found strong correlations between O-Cl chemisorption enthalpies on the surfaces of elemental 3d transition metals, Pd, and Pt, which previously had been shown only for one family of transition metal alloys and binary rutile metal oxides. We first show – using density functional theory (DFT) with various exchange-correlation (XC) functionals and van der Waals (vdW) corrections – that the vdW-uncorrected XC functional based on the generalized gradient approximation of Perdew, Burke, and Ernzerhof (PBE) most accurately reproduces the measured chemisorption energies of O and H on the (111) surface of face-centered-cubic (fcc) Pt. We then, using DFT-PBE, reveal the presence of O-Cl chemisorption scaling relations on surfaces of the 3d transition metals, Pd, and Pt in the fcc and their ground-state bulk crystal structures, indicating that the electronic structure of the metals, rather than any morphological contribution, largely dictates the adsorption properties of these ionic adsorbates. Furthermore, we identified that the O chemisorption energy could be modeled accurately using an extended Born-Haber cycle based on the sum of the first and second ionization energies of the relevant metal atoms. Finally, we synthesize these results in the context of O-Cl chemisorption scaling on transition metal alloys and rutile metal oxides, showing that the differences in the intercepts of their linear scaling relations can be attributed primarily to differences in work functions between metals and metal oxides.