Platinum dissolution potential cycling conditions

Potential cycling conditions accelerate platinum dissolution compared with potentiostatic conditions (Johnson et al. 1970 Rand and Woods 1972 Kinoshita et al. 1973 Ota et al. 1988). For example, Wang et al. (2006a, b) reported that the dissolution rates under potential cycling are 3-4 orders of magnitude higher than... 

It has been demonstrated that STM can operate not only in vacuum but also in air [37] and in electrolytes [38]. For example, Sonnenfeld et al. [37] monitored the in situ deposition of silver on graphite and Arvia et al. [39] monitored the effect of repetitive potential cycling on gold. On the other hand, Fan and Bard [40] studied the in situ STM measurements for the corrosion of stainless steel and the dissolution of nickel under potentiostatic conditions. Szklarczyk and Bockris [41] have published an account of the potential dependence of the crystal reconstruction on platinum in the sodium perchlorate solution at the angstrom scale. The atomic lattice of Al( 111) has been reported... 

By means of a transient ID model. Darling and Meyers [15] studied the kinetics of platinum dissolution under constant load and load cycling conditions. They followed Eqs. (20.5-20.7) assuming that the oxidation of Pt to PtO was the dominant effect and assuming slow kinetics for the chemical dissolution of platinum. The formation of platinum oxide was allowed to exceed one monolayer on the platinum particles, leading to a surface coverage of 6 > 1. This assumption is based on experimental results showing that 0 = 1 is reached at an electrode potential of — 1.15 V [69-71]. Once a PtO monolayer is formed, further dissolution or precipitation of platinum is inhibited. 

In summary, it can be concluded that platinum dissolution and catalyst particle growth are particularly fast during potential transients because of the delayed PtO formation. Furthermore, accelerated oxidation of the carbon support is observed under cycling conditions. These mechanisms result in cell degradation lowering the durability of the fuel cell significantly. 

One critical issue facing the commercialization of low-temperature fuel cells is the gradual decline in performance during operation, mainly caused by the loss of the electrochemical surface area (EGA) of carbon-supported platinum nanoparticles at the cathode. The major reasons for the degradation of the cathodic catalyst layer are the dissolution of platinum and the corrosion of carbon under certain operating conditions, especially those of potential cycling. Cycling places various loads on... 

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