96
[29, 30]. Here, a steady state is attained quickly, and, at steady state, double-layer
charging does not enter the measurement.
The electrode consists of a conductive disk embedded in an inert nonconductive
polymer, usually Teflon
C
or resin, which is mounted on a shaft of electrical rotator
(Fig. 7.13). Polycrystalline metal disk is well polished and cleaned after insertion in
the Teflon holder. Commercial rotating disk electrodes are available from several
manufacturers. Since recent electrocatalysis studies are in large part done with
single- crystal electrodes, requirements for single-crystal rotating electrodes are
growing.
The difficult part of making a single crystal rotating electrode is to preserve an
atomically ordered surface while inserting the crystal into the Teflon holder. Even
more difficult is avoiding contamination of the ordered surface by adsorption of
impurities from air or other environments. Successful procedures have been developed for Au single crystals [31] and for platinum [32]. A hanging meniscus rotating
electrode without a Teflon holder was proposed [33]. The crystal pulled above the
solution level carries a meniscus in contact with the ordered surface. This arrangement does not obey exactly Levich behavior, but may be useful in some studies. For
studies of nanoparticle catalysts, a procedure involving placing on rotating glassy
carbon electrode a very thin layer of nanoparticle catalyst suspended in dilute
Nafion solution in alcohol was proposed [34]. Evaporation of alcohol leaves a very
thin layer of Nafion bonding particles on the carbon disk.
The rotating disk electrode (RDE) is one of the few convective electrode systems
for which the hydrodynamic equations and the convective-diffusion equation have
been solved rigorously for the steady state. When the rate of reaction is under mixed
Fig. 7.13 Schematics of the rotating disc electrode (a), convection currents at rotating disk electrode (b)
7 Platinum Monolayer Electrocatalysts
[29, 30]. Here, a steady state is attained quickly, and, at steady state, double-layer
charging does not enter the measurement.
The electrode consists of a conductive disk embedded in an inert nonconductive
polymer, usually Teflon
C
or resin, which is mounted on a shaft of electrical rotator
(Fig. 7.13). Polycrystalline metal disk is well polished and cleaned after insertion in
the Teflon holder. Commercial rotating disk electrodes are available from several
manufacturers. Since recent electrocatalysis studies are in large part done with
single- crystal electrodes, requirements for single-crystal rotating electrodes are
growing.
The difficult part of making a single crystal rotating electrode is to preserve an
atomically ordered surface while inserting the crystal into the Teflon holder. Even
more difficult is avoiding contamination of the ordered surface by adsorption of
impurities from air or other environments. Successful procedures have been developed for Au single crystals [31] and for platinum [32]. A hanging meniscus rotating
electrode without a Teflon holder was proposed [33]. The crystal pulled above the
solution level carries a meniscus in contact with the ordered surface. This arrangement does not obey exactly Levich behavior, but may be useful in some studies. For
studies of nanoparticle catalysts, a procedure involving placing on rotating glassy
carbon electrode a very thin layer of nanoparticle catalyst suspended in dilute
Nafion solution in alcohol was proposed [34]. Evaporation of alcohol leaves a very
thin layer of Nafion bonding particles on the carbon disk.
The rotating disk electrode (RDE) is one of the few convective electrode systems
for which the hydrodynamic equations and the convective-diffusion equation have
been solved rigorously for the steady state. When the rate of reaction is under mixed
Fig. 7.13 Schematics of the rotating disc electrode (a), convection currents at rotating disk electrode (b)
7 Platinum Monolayer Electrocatalysts