Croatica Chemica Acta, Vol. 90 No. 2, 2017.
Izvorni znanstveni članak
https://doi.org/10.5562/cca3201
Poetics of Interplay and Interferences of Potentiodynamic Sweeps and Peaks in Electrocatalysis for Oxygen Electrode Reactions
Jelena M. Jaksic
; Institute of Chemical Engineering Science, ICEHT/FORTH, Patras, Greece
Caslav M. Lacnjevac
; Faculty of Agriculture, University of Belgrade, Belgrade, Serbia
Milan M. Jaksic
; Institute of Chemical Engineering Science, ICEHT/FORTH, Patras, Greece
Sažetak
Strong irreversible adsorptive monolayer growth of the surface (Pt=O→1), out of the reversible primary (Pt−OH→0) oxides, imposes typical highly pronounced reaction polarization, and that way prevents, at least partially, the reversible electrocatalytic properties and behavior of even all plain and non-interactive supported noble metals (Pt, Pt/C) for oxygen electrode reactions, within closed loop of potentiodynamic spectra between hydrogen and oxygen evolving limits. Substantially quite another type of assembly afford nanostructured hyper-d-electronic-metals (Pt,Au,Ru), interactive grafted upon hypo-d-(f)-oxide supports, in particular of mixed and higher alter-valence values (W,Mo,Ta,Nb), well and for longer known in heterogeneous catalysis as SMSI (Strong Metal-Support Interaction, the ones of strongest in the entire chemistry). The most promising being Magneli phases (MPs, TinO(2n−1), or Ti4O7 in average, and as the optimum in catalytic activity), which arise after simple thermal recrystallization (pure entropy change contribution) yield effect, out of anatase and/or rutile titania (TiO2). The main accompanying achievements of substantial significance then have been: (i) Prevailing percentage in spontaneous adsorptive dissociation of molecular water upon hypo-d-(f)-oxide surfaces, or the corresponding latent storage and spillover of the yielding primary oxides (Pt−OH); (ii) Extra high stability MPs, (Plate type electrodes of MPs are straightforward employed in industrial chlorate cell production, and/or Li-batteries); (iii) Spontaneously adsorptive dissociated water molecules (or, hydroxide ions), then undergo membrane type ionic transfer all along hypo-d-(f)-oxide supports, until approaching catalytic metal surface, when the latter takes the prevailing amount of electron charge, and that way creates the primary oxide dipole species (Pt−OH); (iv) these undergo spillover by repulsion upon metallic, hypo-d-(f)-oxide and even over the suboxide MPs surfaces; (v) while the Magneli phases themselves feature a rather high n-type electron conductivity (up to and even above 1,000 S/cm). The wetness impact factor and effect have been introduced as the lowest threshold level associated with the Pt−OH (Au−OH), bellow which there is no (electro)catalytic oxidation reaction taking place, such as the CO tolerance. The overall result of the present study has then been the development and achievement of the reversible electrocatalysts for the oxygen electrode reactions (ORR, OER), primarily for L&MT PEMFCs.
This work is licensed under a Creative Commons Attribution 4.0 International License.
Ključne riječi
spillover; primary oxide (Pt−OH); surface oxides (Pt=O); Magneli phases (MPs); latent Pt−OH storage; reaction polarization; spontaneous adsorptive dissociation; polarization barrier; CO tolerance
Hrčak ID:
187224
URI
Datum izdavanja:
3.7.2017.
Posjeta: 1.878 *