The Pd()–R27°-O surface oxide revisited

Abstract

The Pd (100) Combining high-resolution core-level spectroscopy (HRCLS), scanning tunneling microscopy (STM) and density-functional theory (DFT) calculations we reanalyze the Pd (100)o -O surface oxide phase. We find that the prevalent structural model, a rumpled PdO(001) film suggested by previous low energy electron diffraction (LEED) work (M. Saidy et al., Surf. Sci. 494, L799 (2001)), is incompatible with all three employed methods. Instead, we suggest the two-dimensional film to consist of a strained PdO(101) layer on top of Pd(100). LEED intensity calculations show that this model is compatible with the experimental data of Saidy et al.

Nanometer and Subnanometer Thin Oxide Films at Surfaces of Late Transition Metals

“…13 exemplifies this with corresponding results for the case of a Pd(100) surface in constrained equilibrium with an O 2 and CO environment. 46 Similar to the aforediscussed situation at Pd(111), oxidation proceeds also at Pd(100) via a trilayer-structured O-Pd-O surface oxide film 35 , that was recently identified as essentially a strained and rumpled layer of PdO(101) on top of the Pd(100) substrate 47 . Although the (101) orientation is not a low-energy surface of bulk PdO, 48 it gets stabilized in the commensurate ( √ 5 × √ 5)R27 o arrangement of the thin oxide film due to a strong coupling to the underlying metal substrate.…”

Near Ambient Pressure XPS Investigation of CO Oxidation Over Pd3Au(100)

“…The √5 surface oxide structure on Pd(100) is well documented [43,53] and is, as stated above, known 105 to be the active phase during CO oxidation in excess oxygen [19] at near ambient conditions. An 106 image of the LEED pattern for this oxide structure obtained by exposing the single crystal surface to 107 O2 at about 10 -5 mbar and ~ 320 °C is shown in Figure 1 (bottom).…”

“…These represent a fingerprint of the √5 surface oxide [43]. In addition, there is an 127 interface component at 334.7 eV that is attributed to Pd atoms in the layer directly underneath the 128 surface oxide [43]. The spectral weights of the 2-fold and 4-fold contributions are similar, indicating a 129 surface with comparable amounts of the two oxygen-coordinated species.…”

“…The presence of the surface oxide during high CO2 production is also 42 supported by kinetic Monte-Carlo simulations [20,21]. 43 Bimetallic systems provide routes for improved catalyst performance through modification of 44 selectivity and activity, demonstrated for example for catalytic oxidation [22] and reforming [23]. 45 Typical alloying elements for Pd based catalysts include among others Cu [24][25][26], Ag [27] and Au 46 [28].…”

“…These represent a fingerprint of the √5 surface oxide [43]. In addition, there is an 127 interface component at 334.7 eV that is attributed to Pd atoms in the layer directly underneath the 128 surface oxide [43].…”