We describe the fabrication of a nanometer-size electrode based on an insulating TiO2 film and a metal nanoparticle (NP). The TiO2 film is deposited on the conducting Pt surface of an ultramicroelectrode (UME) to block electron transfer (ET) to solution species. The film thickness is, however, thin enough to enable tunneling to Pt NPs; thus, the subsequent contact of metal NP to the TiO2 film restores the ET to solution species solely on the NP surface via facile electron tunneling. Consequently, the composite of UME/metal oxide film/NP offers nm-scale active area. The TiO2 film is electrochemically deposited on the Pt UME (Pt UME/TiO2), monitoring the cyclic voltammetry (CV) of ferrocenemethanol until the oxidation wave just disappears. A single Pt NP is captured in a collision experiment by observing the current increase upon contact of the Pt NP with the Pt UME/TiO2 by means of Pt NP-mediated electrochemical reduction of Fe(CN)6(3-). The resultant Pt UME/TiO2/Pt NP (or tunneling UME, T-UME) showed long-term stability and robustness with well-defined electrochemical response, suggesting applicability as a novel nm-size electrode for CV and steady-state measurements such as those with scanning electrochemical microscopy (SECM). Here, we employed the T-UME to measure SECM approach curves and showed remarkable approach capability for a nm-size SECM probe.
We report that oxide composite electrodeposition can be used for the facile preparation of metal-doped BiVO 4 photoelectrodes for photoelectrochemical water oxidation. The photoactivity of electrodeposition film was improved by the addition of a small amount of tungstic acid particles during the electrodeposition. These particles are incorporated in the deposit and finally generate tungstendoped bismuth vanadate. The suspended particles in the plating solution were electrostatically attracted to the cathode and accordingly incorporated into the deposit (electrostatic deposition). WO 3 nanoparticles (NPs) can be used instead of tungstic acid, to yield a BiVO 4 with different properties. Enhanced photoelectrochemical (PEC) water oxidation was confirmed via scanning electrochemical microscopy (SECM) by detecting increased oxygen evolution with using optical fiber incorporating a ring electrode.
Silicium für Solarzellen: Relativ reines, polykristallines und photoaktives Silicium wurde direkt aus Quarznanopartikeln (NP) durch Elektroabscheidung auf einer Silberelektrode in geschmolzenem CaCl2 erhalten (siehe Bild). Dieser Prozess basiert auf der Bildung einer Silber‐Silicium‐Legierung und der Reduktion von Quarz zu Silicium. Das abgeschiedene Silicium zeigt bei photoelektrochemischen Messungen ein p‐artiges Verhalten.
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