Influence of Graphene on Charge Transfer between CoPc and Metals: The Role of Graphene–Substrate Coupling

Abstract

The electronic structure of cobalt phthalocyanine (CoPc) on Pt(111), graphene/Pt (111), and Au-intercalated graphene/Ni(111) is investigated by photoexcited electron spectroscopies: photoemission (XPS and UPS) and X-ray absorption spectroscopy (XAS or NEXAFS). For CoPc on Pt(111), significant changes of the shape of XPS and XAS spectra indicate a charge transfer from the metal substrate to the Co ion of CoPc. The strong interaction between CoPc and Pt(111) can be completely prevented by the insertion of a graphene buffer layer. For CoPc on graphene/ Ni(111), the charge transfer is only prevented if the graphene on Ni(111) is intercalated by gold. Therefore, the disturbance of the graphene electronic structure by the interaction with underlying substrate and the corresponding charge doping of graphene has been found to affect the electronic properties of adsorbed CoPc considerably.

Exploring the Effect of Gold Support on the Oxygen Reduction Reaction Activity of Metal Porphycenes

“…Bader charge analysis shows net charge transfer from the support to the MPc molecule (see section S4 in ESI). Similar charge transfer between Co and Mn−pthalocyanines and the underlying metallic support has earlier been observed experimentally ,. The difference in electron density due to the molecule‐support interaction suggest a surface coordinative bond between the metal in MPc and the gold atom nearest to the metal.…”

“…Interestingly, transition metal porphyrins and similar molecular complexes are known to self‐assemble on coinage metal supports . Several studies have been devoted towards understanding the molecule‐support interaction of transition metal–porphyrins or pthalocyanines on supports such as gold, silver, copper, platinum or even non‐metal surfaces such as graphene,, graphene oxide,, and carbon nanotubes ,,. Depending on the strength/nature of the interaction between metal surface and organometallic homogeneous catalyst, the charge, spin, or magnetism of the adsorbed molecular catalyst can be modified which in turn may influence its catalytic properties …”

FePc and FePcF16 on Rutile TiO2(110) and (100): Influence of the Substrate Preparation on the Interaction Strength

“…In Figure 8, we compare the intensity ratio between features A and C of the N-K absorption spectra of FePc and CoPc on several substrates as a function of the film thickness. The data were taken from [13,25,27,42,43]. Like in Figure 7, we analyzed spectra recorded at grazing incidence, since for most systems at this geometry, the N 1s-π * transitions are strongest due to the preferred flat lying molecular orientation on the substrate surfaces.…”

“…Comparison of relative intensities of transitions into π * -orbitals in N-K edge X-ray absorption spectra of FePc and CoPc and on several substrate surfaces as a function of the film thickness. Data from[13,25,27,42].…”

Unveiling orbital coupling at the CoPc/Bi(111) surface by ab initio calculations and photoemission spectroscopy

“…According to previous reports, the major component located at 780.6 eV should be regarded as the characteristic of the Co(II) oxidation state, 50,51 which arises from the original CoPc in gas phase. 52 Interestingly, another intense peak is visibly recognized at the binding energy of 778.5 eV, which shall be attributed to the cobalt metal state (Co(0)). 50,51 The emergence of Co metal state upon adsorption on Bi(111) herein can only be assigned to the interfacial charge transfer and the related molecule-substrate interaction, which make the original partial-empty Co 3d state (for example, the d z 2 orbital) lled and consequently, a new chemical state located at lower binding energy is resolved.…”