Oxygen reduction, at platinum

Similar size effects have been observed in some other electrochemical systems, but by far not in all of them. At platinized platinum, the rate of hydrogen ionization and evolution is approximately an order of magnitude lower than at smooth platinum. Yet in the literature, examples can be found where such a size effect is absent or where it is in the opposite direction. In cathodic oxygen reduction at platinum and at silver, there is little difference in the reaction rates between smooth and disperse electrodes. In methanol oxidation at nickel electrodes in alkaline solution, the reaction rate increases markedly with increasing degree of dispersion of the nickel powders. Such size effects have been reported in many papers and were the subject of reviews (Kinoshita, 1982 Mukerjee, 1990). 

Sepa DB, Vojnovic MV, Damjanovic A. 1981. Reaction intermediates as a controlling factor in the kinetics and mechanism of oxygen reduction at platinum electrodes. Electrochim Acta 26 781-793. 

Damjanovic A, Genshaw MA, Bockris JO M. 1967. The mechanism of oxygen reduction at platinum in aUcahne solutions with special reference to H2O2. J Electrochem Soc 114 ... 

SepaDB, VojnovicMV, VracarLj. M, Damjanovic A. 1986a. Apparent enthalpies of activation of electrodic oxygen reduction at platinum in different current density regions—1. Acid solution. Electrochim Acta 31 91-96. 

M. Van Brussel, G. Kokkinidis, A. Hubin, and C. Buess-Herman, Oxygen reduction at platinum modified gold electrodes, Electrochirrr Acta 48,3909-3919 (2003). 

In a catalytic reaction, all steps do not equally depend on the surface structure. So, for example, the rate of simple desorption processes is often not markedly affected by the structure of the surface. In catalysis, therefore, reactions are classified into "structure sensitive" and "structure insensitive" [5], usually on the basis of the variation of reactivity with particle size. As an example, the electrocatalytic oxygen reduction at platinum (which is of importance for fuel cells) will be mentioned, where a decrease of specific activity with increasing particle size was reported [6,7]. In a theoretical analysis [8], the kinetics was treated on the (111), (10 0), and (211) facets of several transition metals, and the results were combined with simple models for the geometries of catalytic nanoparticles. Thus, the experimentally observed trend could be well reproduced. 

Sepa, D. B. Vojnovic, M. V. Vracar, L. M. Damjanovic, A. Different views regarding the kinetics and mechanisms of oxygen reduction at platinum and palladium electrodes. Electrochim. Acta 1987,32,129-134. 

Kongkanand A, Kuwabata S. Oxygen reduction at platinum monolayer islands deposited on Au(lll). J Phys Chem B 2005 109(49) 23190—5. 

Sawyer DT, Day RJ (1963) Kinetics for oxygen reduction at platinum, palladium and silver electrodes. Electrochim Acta 8 589-594... 

Pletcher D, Sotiropoulos S (1993) A study of cathodic oxygen reduction at platinum using microelectrodes. J Electroanal Chem 356(1-2) 109-119... 

Damjanovic, A., Genshaw, M. and Bockris, J. (1967). The Mechanism of Oxygen Reduction at Platinum in Alkaline Solutions with Special Reference to HoOo, J. Electrochem. Soc., 114, pp. 1107-1112. 

Johnson L, Ejigu A, Licence P, Walsh DA (2012) Hydrogen oxidation and oxygen reduction at platinum in protic ionic Uquids. J Phys Chem C 116(34) 18048-18056. doi 10.1021/... 

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