X-Ray Photoelectron Spectroscopy Study of the Composition of Polyphenol Films Formed on Pt by Electropolymerisation of Phenol in the Presence of Sulphide in Carbonate Medium

Abstract

ABSTRACT:The chemical composition and structure of polyphenol films formed electrochemically on Pt from bulk phenol in the absence and in the presence of solution sulphide were studied by XPS. The C1s (284.2-284.6 and 285.6-286 eV) and the O1s (533 eV) signals are consistent with a polymeric structure consisting of an aromatic carbon ring backbone linked by ether-like bonds and with hydroxyl groups. This structure is common to all the examined films formed under either potentiodynamic or potentiostatic conditions, even though the coatings formed in the presence of sulphide seemed to possess a higher ether-like oxygen content. Polyphenol films generated by cyclic voltammetry in the presence of sulphide contained a small amount of incorporated sulphur, with a characteristic binding energy of 162.3 eV which is essentially identical to that found for a sulphur layer deposited on Pt from sulphide in phenol-free solutions. The film is described as a S-polyphenol composite material, in which the S fraction is mainly incorporated at the early stages of filming. Sulphur-polyphenol composite coatings proved to possess more effective barrier properties than S-free polyphenol films.KEY WORDS Cyclic Voltammetry / X-Ray Photoelectron Spectroscopy / Sulphur / PPO / Corrosion Inhibition / Barrier Film / Protective coatings made of certain conducting or insulating polymeric films (or a blend of both) have proved to be effective against metallic corrosion. 1-6 Conducting polymeric films can impart active protection by exchanging electrons with the metallic substrate, generally pushing the corrosion potential into the passive region. This fact is not, however, sufficient for a successful protection. Tight adherence to the surface, high mechanical strength, film integrity and insolubility are mandatory requisites. Many insulating polymers meet these requirements and, provided they behave as strong physical barriers against corrosive electrolyte penetration, can effect satisfactory protection degrees. Despite their non-electroactive nature, thin insulating films can be formed onto metallic or semiconducting substrates by electropolymerisation from the bulk monomer, before dielectric properties manifest and the film growth is inhibited. Thus, the coating process can also benefit from the advantages of electrochemical methods, namely, simplicity, and flexibility of the experimental apparatus, efficient coating of not readily accesible areas and higher homogeneity of the films.Among insulating polymers, polyphenol films (also called polyoxyphenylene, poly(phenylene) oxide or PPO films) have received much attention. 1, 2, 7-20 These films were electropolymerised from phenol or phenol derivatives in a wide variety of electrolytic media, ranging from organic 9, 17 to hydroalcoholic 1, 2, 7, 10 to aqueous solutions 8,[12][13][14][15][16][18][19][20] at various pH. The role of several ring substituents was checked in order to increase the monomer solubility in the working electrolyte, to direct the oxidative coupling mechanism to desired ri...

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“…In detail, two broad peaks at binding energy of about 458.6 eV and 464.2 eV were observed in Figure (b), corresponding to the characteristic Ti 2p 1/2 and Ti 2p 3/2 peaks of Ti 4+ , respectively . In Figure (c), two C 1s peaks centered at 284.7 eV and 285.8 eV can be attributed to C‐C bonds and C‐O ether bonds, corresponding to aromatic carbon and chain propagation within PPO, respectively, which was in agreement with electrodeposition of PPO on Pt or Fe electrode . In Figure (d), O 1s core peak was composed of three main peaks at 531.0 eV (C‐O), 529.8 eV (Ti‐O) and 532.9 eV (O‐H hydroxyl), corresponding to oxygen in PPO and TiO 2 NT, respectively …”

The Nature of the Electro‐Oxidative Catalytic Response of Mixed Metal Oxides: Pt‐ and Ru‐Doped SnO2 Anodes

“…During the course of progressive cycling towards higher positive potentials, both electrodes display a gradual decrease in the current density associated to phenol electro‐oxidation, thus indicating a progressive deactivation of the electrode for this process ,,. This surface fouling is related to the formation/deposition of passivating films of oligomeric or polymeric nature . In addition, the pairs of reduction and oxidation processes develop to reach a maximum current.…”

Fabrication of TiO2 Micropatterns on Flexible Substrates by Vacuum‐Ultraviolet Photochemical Treatments

“…To investigate the chemical states of the remaining inorganic films, XPS measurements were carried out by acquiring C1s, O1s, and Ti2p spectra, as shown in Figure . Deconvolution of the C1s spectra indicated that oxygenated carbon species corresponding to binding energies of ≈284.8 eV for CC, ≈286.0 eV for CO, ≈287.2 eV for CO, and ≈289.1 eV for OCO [ 48–50 ] were clearly decreased by the VUV/(O) treatment. These results are consistent with the results of FTIR.…”