A Photoelectron Spectroscopy Study on the Interfacial Chemistry and Electronic Structure of Terephthalic Acid Adsorption on TiO₂(110)-(1×1) Surface

Abstract

The chemical bonding mechanism, electronic structure, and the energy level alignment at the terephthalic acid (TPA)/TiO2 (110)-(1×1) interface were investigated in situ by means of X-ray photoelectron spectroscopy (XPS) and synchrotron radiation photoemission spectroscopy (SRPES). It has been found that the adsorption of TPA on TiO2(110)-(1×1) at room temperature leads to the formation of dicarboxylate species at lower coverage (∼0.2 ML) followed by the formation of monocarboxylate species below 1 ML, indicating a geometry variation from flat-lying to upright adsorption. Further deposition of TPA onto the first monolayer results in a multilayer growth without deprotonation. The energy level alignment at the TPA/TiO2 (110) interface demonstrates a straddling lineup of the organic frontier molecular levels with respect to the oxide bands at the interface. A large energy difference with a value of ∼1.1 eV is present between the lowest unoccupied molecular orbital (LUMO) of TPA and the conduction band (CB) of TiO2, suggesting an energetically favorable electron transfer from TPA into TiO2. Fundamental understanding of the chemical interactions and electronic properties at the TPA/TiO2 interface could facilitate unravelling the microscopic mechanism for interfacial charge transfer dynamics, which is desirable for exploring a new generation of hybrid energy devices.

Electronic structures of bare and terephthalic acid adsorbed TiO2(110)-(1 × 2) reconstructed surfaces: origin and reactivity of the band gap states

“…In this sense, f of the (1 Â 2) surface appears to stabilize at B0.5 ML, while the (1 Â 1) surface tends to be stable at B1 ML, suggesting that the saturated chemisorption coverage on the (1 Â 2) surface is nearly half that on the (1 Â 1) surface. 6,30 The variation of the Ti 3+ /Ti 4+ ratio usually characterizes the occurrence of charge transfer or chemical reactions at the surface. In this model, half of the five-fold coordinated Ti 4+ sites present on the original (1 Â 1) surface are covered with Ti 2 O 3 strings, and due to the outmost oxygen termination, the molecular adsorption on these strings is hindered, thus resulting in the half coverage of the saturated chemisorption on the (1 Â 2) surface with respect to the (1 Â 1) surface.…”

“…30 The TiO 2 (110) wafer (10 Â 5 Â 0.5 mm 3 , supplied by KMT Ltd, China) was preprocessed by repeated Ar + sputtering (1 keV, 10 mA, 10 min) and subsequent annealing at 870 K for 20 min. The beamline provides the photon energy ranging from 10 to 250 eV, an interval particularly suitable for the excitations of valence electrons.…”

“…The electronic structures of the TPA/TiO 2 (110)-(1 Â 2) interface, specifically the origin of BGSs and its response to TPA adsorption have been investigated in combination with density functional calculations. [28][29][30] 26,27 Furthermore, benzoic acids are liable to form well-ordered monolayers on the TiO 2 (110) surface.…”

Chemical nature and thermal decomposition behavior of tartaric acid multilayers on rutile TiO2(110)

“…As a matter of fact, unlike what is observed for RR-TA molecules and other carboxylic acids adsorbed on Cu(110), 24,[33][34][35][36] components of carboxylate and carboxylic C atoms are not resolved on TiO 2 (110), as previously observed for terephthalic acid adsorption on the same rutile surface. 37 Despite the superposition of COO − and COOH contributions on TiO 2 (110), information on the evolution of RR-TA chemical form may still be gained by considering the energy splitting between peaks F and G and the relative variation of their FWHM. Some constraints are used for the fit, namely, the intensity ratio F/G = 1, according to the molecular stoichiometry, and the FWHM of peak F, since no variation is expected for this peak which is related to the central C-OH carbon atoms.…”

A Surface Study of Ultrathin Ceria Nanoparticles Decorated with Transition‐Metal Ions

“…The main surface characterization techniques include electron spectroscopy methods such as Auger electron spectroscopy (AES) and X‐ray photoelectron spectroscopy (XPS), ion‐based methods such as secondary‐ion mass spectrometry (TOF‐SIMS) and low‐energy ion scattering (LEIS), and scanning probe microscopy (e.g., atomic force microscopy (AFM) and scanning tunneling microscopy (STM)) . In the characterization of modified surfaces, XPS, in particular, is a common method for the determination of the oxidation states of the dopant as well as for the estimation of the dopant coverage . In many cases, the examined NPs do not have surfactants at their surface, leading to high quality of the results.…”