Properties Of Pt Electrode Research Articles

Iodonium-based pro-adhesive layers for robust adhesion of PEDOT:PSS to surfaces

ABSTRACT Electrochemical grafting of organic molecules to metal surfaces has been well-known as an efficient tool enabling tailored modification of surface at the nanoscale. Among many compounds with the ability to undergo the process of electrografting, iodonium salts belong to less frequently used, especially when compared with the most popular diazonium salts. Meanwhile, due to their increased stability, iodonium salts may be used in situations where the use of diazonium salts is constrained. The aim of this study was to examine the effect of the electrochemical reduction of iodonium salts on the physicochemical properties of Pt electrodes, and the possibility to form pro-adhesive layers facilitating further functionalization purposes. Consequently, we have selected four commercially available iodonium salts (diphenyliodonium chloride, bis(4-tertbutylphenyl)iodonium hexafluorophosphate, (4-nitrophenyl)(2,4,6-trimethylphenyl)iodonium triflate, bis(4-methylphenyl)iodonium hexafluorophosphate), and attached them to the surface of Pt electrodes by means of an electrochemical reduction process. As-formed layers were then extensively characterized in terms of wettability, roughness and charge transfer properties, and used as pro-adhesive coatings prior to the deposition of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate), PEDOT:PSS. Due to the increase in hydrophilicity and roughness, modified electrodes increased the stability of PEDOT:PSS coating while maintaining its high capacitance.

Research on Electrode Propertie of Heater for Planar Oxygen Sensor

Through screen-printing technology, we prepared heater which is used for planar oxygen sensor with YSZ solid electrolyte, alumina insulating layer and platinum(Pt) paste, then sintered at different temperatures.Analysis the properties of Pt electrode through aging time test and thermal shock test. The results show that 1100°C is the best sintering temperature for Pt electrode.Resistance and surface morphology of Pt electrode changed obviously with aging time increasing and 100 times thermal shock is not enough to affect the morphology of electrode and the change of resistance has no regularity.

The resting-state of the Pt-black electrode in acid solution and the structure of the adsorption layer. Coulometric and electrochemical quartz crystal microbalance measurements

The properties of Pt-electrodes in 1 M HClO 4 solution, in air, were studied both in the resting-state and mild oxidation conditions, within the potential range of 1000 mV and 1600 mV. Cyclic voltammetry (CV) and cathodic stripping voltammetry (CSV) were used for coulometric determination of the amount of O-containing species adsorbed on the electrode surface during the oxidation–reduction reactions. Simultaneously, the mass of the adsorption layer was measured in situ, with the electrochemical quartz crystal microbalance (EQCM). The surface of the Pt-black electrode in the resting-state is covered with OH*-species (apparently a ML), which are spontaneously generated by immersion in the aqueous solution without any polarization potential. The surface of the Pt smooth electrode is covered uppermost by a sub-monolayer of oxygen, in similar conditions. The resting-state of the Pt-black electrode is characterized by a reproducible value of the rest potential, E r = 1040 ± 5 mV (average of 10 samples) and a reduction peak in CV mode at E ′ p = 791 ± 7 mV (average of 10 samples). In anodic polarization conditions, PtOH* is oxidized to PtO*, in CV mode, and to Pt(O 2)*, in the potentiostatic mode. The reduction peak of PtO* in CV mode is E ″ p = 694 ± 9 mV (average of 10 samples), indicating a stronger bond to the surface of the electrode. The yielding of Pt(O 2)* is not fast enough to accommodate the increase of the oxidation potential by finite sweep rate of the CV mode at 10 mV s −1. Therefore this oxidation level could not be achieved in CV mode. The prolonged oxidation in the potentiostatic mode results in the coverage of the surface of Pt-black electrode with a monolayer of (O 2)*-species.

INFLUENCE OF ADHESION LAYERS ON THE SURFACE MORPHOLOGY OF PLATINUM-BASED BOTTOM ELECTRODES FOR Pb(Zr,Ti)O3 THIN FILMS

A thin adhesion layer is required to glue Pt bottom electrodes of ferroelectric Pb(Zr,Ti)O 3 thin films to a SiO 2/ Si wafer. Here we report the effect of adhesion layers, Ti and TiO 2, on the crystalline structure and surface properties of Pt electrode. The results show that the hillock formation is observed for the case of Ti glue layer, while the surface of Pt layer is flat and uniform with TiO 2 layer used instead. The crystallization in PZT thin films on Pt / TiO 2/ SiO 2/ Si substrate is investigated during post-deposition annealing. The perovskite phase is completely formed in the film annealed at 650°C for one hour.

Influence of Adhesion Layers on the Surface Morphology of Platinum-based Bottom Electrodes for Pb(Zr,Ti)O<SUB>3</SUB> Thin Films

A thin adhesion layer is required to glue Pt bottom electrodes of ferroelectric Pb(Zr,Ti)O3 thin films to a SiO2/Si wafer. Here we report the effect of adhesion layers, Ti and TiO2, on the crystalline structure and surface properties of Pt electrode. The results show the hillock formation is observed for the case of Ti glue layer, while the surface of Pt layer is flat and uniform with TiO2 layer used instead. The crystallization in PZT thin films on Pt/TiO2/SiO3/Si substrate is investigated during post-deposition annealing. The perovskite phase is completely formed in the film annealed at 650oC for one hour.

Effects of Ionic Conductivities of Zirconia Electrolytes on Polarization Properties of Platinum Anodes in Solid Oxide Fuel Cells

To find a clue for the design of high-performance electrodes for solid oxide fuel cells (SOFCs), the polarization properties of Pt electrodes attached to zirconia electrolytes with various ionic conductivities were investigated at 800-1000[degree]C. The IR-free anodic polarization in hydrogen was greatly affected by the ionic conductivity of the electrolyte, and it obeyed the Tafel equation. The exchange current density increased in proportion to the square of the ionic conductivity for all electrolytes operated at 800-1000[degree]C, while the transfer coefficient (n[alpha][sub o] = 2) was independent of the temperature and of the conductivity of electrolytes. According to our analysis, the rate-determining step is not a simple electron transfer from oxide ions but a recombination step involving discharged oxygen atoms adsorbed on the Pt electrode/electrolyte interface; an increase in the rate of transport of oxide ions to the interface, for example, by using an electrolyte with higher-ionic conductivity, reduces the anodic overpotential greatly. 34 refs., 6 figs., 1 tab.

Determination of adsorption of OPD H species in the cathodic hydrogen evolution reaction at Pt in relation to electrocatalysis

The coverage and pseudocapacitance behaviour of overpotential-deposited (OPD) H species in the cathodic H 2 evolution reaction (HER) at Pt electrodes has been determined by the “potential-decay” method, coupled with prior steady-state current measurements. The Tafel slopes and mechanisms of the HER at Pt in acid and alkaline solutions are rationalized in terms of the observed OPD H coverage behaviour in relation to a parallel pathway of electrochemical and recombination-controlled desorption steps. The best electrocatalytic activity of Pt electrodes for the HER arises in acid solutions where the nominal extent of measured OPD H coverage is found to correspond to the apparent formation of ca. 8 equivalent monolayers; one possible interpretation of this result is in terms of hydride formation in the near-surface region of Pt. As a result, the OPD M-H adsorption bond can be weakened so that the recombination step with low Tafel slope becomes the favoured desorption step and characterizes the kinetics at active Pt electrodes. The OPD H coverage and the related electrocatalytic properties of Pt electrodes for the HER, depend strongly on the “activity” or “cleanliness” of the electrode surface with respect to adsorbed impurities.

Electrochemical Studies in Liquid and Solid AgBr

The comparative electrochemical properties of Pt electrodes have been studied in liquid at 429°C and solid at 300°–417°. At all temperatures, a significant time range of ideal polarization kinetics was observed. The intrinsic double‐layer capacitance is the same for liquid and solid and is constant over the solid‐state temperature range investigated. In addition, the principal characteristics of Ag submonolayer deposition are the same above and below the melting point. The results indicate the electrochemical properties are determined by an interfacial ion layer whose characteristics are independent of the state of the electrolyte. Decreasing double‐layer charging rates were observed with decreasing solid‐state temperature and are attributed to interface strain due to differential thermal contraction.