Single-electrode thin layer technique

As examples, experimental F(E) isotherms at = constant for Pb and T1 UPD in acidic perchlorate electrolyte on AgQikl) single crystal faces with Qtkl) = (111) and (100) are shown in Figs. 3.9 and 3.10, respectively [3.97, 3.105]. These isotherms were measured stepwise, waiting for equilibrium conditions according to polarization routines illustrated in Fig. 3.11 using the twin-electrode thin-layer technique" (TTL) for Pb UPD and the flow-through thin-layer technique" (FTTL) for T1 UPD. 

Gulla et al. reported several thin-layer electrodes with superior performance and stability. Using a dual-ion beam-assisted deposition technique, they coated a Pt outer layer ( 50 nm thick, 0.08 mg Pt/cm ) directly onto GDLs with either a Co or Cr inner layer ( 50 nm thick). These bilayered electrodes showed a mass-specific Pt activity more than 50% higher at 900 mV than that for a single Pt layer on GDLs. No ionomers were present in the electrodes. 

Gulla et al. have demonstrated superior performance and stabUily of carbonless thin layer electrodes made by a dual ion beam assisted deposition (IBAD) technique that combines physical vapor deposition (PVD) with ion beam bombardment [47]. They found that bilayered coatings on GDL with either a Co or a Cr iimer layer ( 50 nm thin) and a Pt outer layer ( 50 nm thin, and 0.08 mg Pt cm ) showed a more than 50% higher Pt mass activity at 900 mV than a Pt single layer. 

In the gravimetric method, the adsorbent (usually in the form of powder) is placed into a bulb, which is mounted on a sensitive balance and the bulb is then evacuated. Next, the weight increase of the adsorbent solid as a function of the absorptive gas pressure is monitored at constant temperature. More recently, the quartz crystal microbalance (QCM) technique has been applied this is very sensitive to mass increases. Quartz is a piezoelectric material and the thin crystal can be excited to oscillate in a traverse shear mode at its resonance frequency when a.c. voltage is applied across the metal (usually gold) electrodes, which are layered on two faces of the crystal. When the mass on the crystal increases upon adsorption, its resonance frequency decreases. The increase in the mass is calculated from the reduction in resonance frequency. On the other hand, adsorption on single flat surfaces can also be measured by ellipsometry, which measures the film thickness of transparent films optically using the difference between light reflection from bare and adsorbed surfaces. 

However, ultra-thin films of unsubstituted polyaniline deposited on ITO glass electrode produced by dip coating, spin coating and the LB technique showed the most informative voltammetric characteristics. The single-layer LB films of polymer showed much better and reversible electrochromic activity on repeated scanning within up to 0,9 V in 1,0 M HCl solution than in electrochemically prepared materials [287],... 

Regarding surface spectroelectrochemistry, the intense interest in the electrochemistry of single crystal surfaces, adatoms, oxide layers, and monolayers in the last decade has seen not only the enhancement of traditional methods (e.g., infrared (IR) and Raman microspectroscopy) but also the development of relatively new surface specific methods such as second-harmonic generation, sum-frequency generation, surface plasmon resonance (SPR), and surface-enhanced resonance spectroscopy (SERS). The increased access to synchrotron radiation has led to X-ray absorption and X-ray diffraction methods becoming more feasible as in situ techniques for thin films or species generated close to the electrode. In this article, for... 

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