Characterized Semiconductor Electrodes: I . Effect of Processing Variables on the Photoelectrochemical Properties of Single Crystal (Rutile)

Abstract

The photoelectrochemical behavior of TiO2 (rutile) electrodes has been investigated as a function of electrode preparation. Mechanical polishing of the electrodes has been found to introduce a disturbed layer on the order of 1 μm deep. The experimental results indicate that this layer has an increased density of recombination sites. In addition, this layer affects the reduction process by which donors are created in TiO2 . Etching or annealing this layer can remove it or modify its behavior. The behavior of etched and annealed electrodes indicates that the absorption and/or reflection of light by TiO2 can be affected by electrode processing. The stability of TiO2 electrodes is discussed in terms of their usefulness in electrochemical studies.

Scanning Probe Microscopic Characterization of Surface-Modified n-TiO2 Single-Crystal Electrodes

“…The (001) polished face (10 × 10 × 1.5 mm 3 ) of a single-crystal TiO 2 with the rutile phase, purchased from Earth Chemical Co., Ltd., was provided for surface modification and photoelectrochemical measurements. The TiO 2 crystal was doped by reduction in hydrogen flow at 550 °C for 2 h. , The doped n -TiO 2 surface was modified by lapping or chemical-etching processes. The (001) face was lapped with a 1 μm diamond slurry while keeping the n -TiO 2 crystal fixed in a certain position against a rotating table using a Musashino Denshi MS-2 polishing machine.…”

“…Among three crystal phases of TiO 2 , , photocatalytic activity has been extensively studied for anatase particles while a number of photoelectrochemical experiments with single-crystal TiO 2 electrodes have been carried out using rutile. Since intrinsic TiO 2 crystals have high electrical resistance due to its wide band-gap energy (e.g., 3.0 eV for rutile), they are doped by reduction to have n -type semiconduction for electrochemical applications. − To prepare single-crystal TiO 2 electrodes, the surface is then etched to remove contamination and damage caused by polishing and doping …”

Sol−Gel Synthesis, Electrochemical Characterization, and Stability Testing of Ti0.7W0.3O2 Nanoparticles for Catalyst Support Applications in Proton-Exchange Membrane Fuel Cells

“…Hence, doped TiO 2 has the possibility of being both electrically conducting and kinetically stable under fuel cell conditions, assuming that the doping does not radically alter the chemical stability of the host lattice. Some transition metal oxides have been studied as electrodes or supports in a variety of electrochemical systems. ,− …”

Charge transfer reductive doping of single crystal TiO2 anatase

“…The reaction, once performed in aprotic solvents, follows the scheme Ti 4þ +e À () Ti 3þ accompanied by the uptake of charge compensating cation (usually Li þ ) [8]. In aqueous electrolyte solution however, the reaction is often thought to resemble thermal TiO 2 reduction in a hydrogen atmosphere, where the doping proceeds reportedly [9] via neutral hydrogen atoms inserted into the TiO 2 lattice as mobile donor sites, acting at the same time as the reductive agent. The hydrogen is expected to be formed by proton reduction at the TiO 2 electrode/electrolyte interface [10][11][12][13].…”