Environmental Engineering Reference
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Figure 11.17 Linear cyclic voltammograms of a-FePc/C (——) and b-FePc ( - - - )
recorded in an O 2 -saturated electrolyte (0.5 M H 2 SO 4 , temperature 20 8C, sweep rate 5 mV s 21 ,
rotation speed 2500 rev min 21 ).
control of the adsorption of the oxygen species by the Langmuir isotherm [Sepa et al.,
1986a]. The explanation for the existence of two Tafel slopes is somewhat different at
a-FePc; however, different adsorption modes of molecular oxygen are certainly
involved. One explanation could be the capability of a-FePc to form both PcFe -
O 2 - FePc m-oxo species, allowing breaking of the O - O bond, and FePc - O 2
peroxo species [Baranton et al., 2006]. The difference in catalytic behavior between
the two forms of FePc crystals can then be explained by the catalyst structure. It is
Figure 11.18 Linear cyclic voltammograms of a FePc/C disk electrode and corresponding
oxidation current of a Pt ring electrode maintained at 1.2 V vs. RHE, recorded at 2500 rev
min 21 in an O 2 -saturated 0.5 M H 2 SO 4 electrolyte (temperature 20 8C, sweep rate 5 mV s 21 ).
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