Support and Particle Size Effects in Electrocatalysis - Fuel Cell Catalysis: A Surface Science Approach - page 571

Figure 16.7 Specific activity for oxygen reduction at 0.3 V vs. RHE on carbon- and titania-
supported Au nanoparticles [Guerin et al., 2006b]: (a) C/Au; (b) TiO x /Au. In the case of
TiO x /Au (b), results are shown for data obtained on arrays of electrodes (S) and on rotating
disk electrodes (RDE) (O).
[Hayden et al., 2009]. Figure 16.8 (Plate 16.1) shows the effect of the equivalent thick-
ness of deposited Pt on titania on the activity of the ORR carried out in a 0.5 M HClO 4
electrolyte at 20 8C. In this case, the activity was assessed by determining the potential
(vs. RHE) at which the specific current density reaches 0.01 mA cm 22 : A lower poten-
tial indicates a higher overpotential required to achieve this rate of reaction, and hence
corresponds to a reduction in activity. The shaded region of the plot, below about 1 nm
equivalent thickness, corresponds to coverages over which distinct particles are
Figure 16.8 Pt/TiO x -catalyzed oxygen reduction potential, where 0.01 mA cm 22 is reached
during the negative scan in a cyclic voltammetry experiment (scan rate 20 mV s 21 ) in oxygen-
saturated 0.5 M HClO 4 at 25 8C. (See color insert.)