INVESTIGADORES
FERNANDEZ Jose Luis
artículos
Título:
Evaluation of the intrinsic kinetic activity of nanoparticle ensembles under steady-state conditions
Autor/es:
CYNTHIA G. ZOSKI; JOSÉ L. FERNÁNDEZ; KASUN IMADUWAGE; DULAN GUNASEKARA; RAGHUVEER VADARI
Revista:
JOURNAL OF ELECTROANALYTICAL CHEMISTRY - (Print)
Editorial:
ELSEVIER SCIENCE SA
Referencias:
Lugar: Amsterdam; Año: 2011 vol. 651 p. 80 - 93
ISSN:
1572-6657
Resumen:
This work reports
theory and strategies for evaluating the intrinsic kinetic activity
for oxygen reduction at Pt nanoparticle (NP) ensembles on a large
glassy carbon electrode (GCE) under steady-state conditions. Pt NPs
were synthesized using reverse microemulsions which facilitated the
deposition of random ensembles of bare NPs with controlled NP mean size
and coverage. Steady-state voltammograms
(SSVs) for oxygen reduction were recorded for various NP ensembles with
different NP size and coverage. The effects of NP coverage and mass-transport rate on SSV features were analyzed. For
SSVs normalized with respect to their limiting current, more negative
potentials are needed to reach the limiting current region and the i-E slope decreases as NP coverage decreases. For
those normalized SSVs having unequal limiting currents, the kinetic
rate relative to the mass transport rate changes and plays a role in
the decreasing steepness of the SSV. In
contrast, normalized SSVs recorded under the same mass transport
conditions and decreasing NP coverage are displaced negatively along
the potential axis without a change in the i-E slope.
Normalized SSVs recorded using the same mass transport conditions on
electrodes with similar fractions of inactive area but different NP
sizes were found to be similar. Tafel plots were constructed by processing the SSVs either directly through the use of the electroactive surface area AES
or indirectly through a two-step procedure that uses the geometric
surface area where an apparent potential-dependent kinetic current
density jKapp(E) is first calculated. These two approaches are equivalent and the resulting kinetic current density jK(E) dependencies were shown to be equivalent. The direct method is applicable when AES can be determined whereas the indirect approach is useful when the measurement of AEAS is not possible, but information relating to the fraction of active or inactive area is available.