Oxygen redox reactions

For illustrations, we compare the transfer of anodic holes at metal electrodes and the transfer of anodic photoexdted holes at n-type semiconductor electrodes for the oxygen redox reaction shown in Eqn. 10-16 ... 

Figure 10-30(c) applies to the photoexcited cell, where oxj en evolution proceeds via the anodic transfer of holes at the n-type anode and hydrogen evolution proceeds via the cathodic transfer of electrons at the p-type cathode. In order for the photoelectrolytic decomposition of water to proceed in such a cell, the edge level of the valence band sCy of n-type anode needs to be lower than the Fermi level tr(02ai20) of oxygen redox reaction and the edge level of the conduction band p c of p-type cathode needs to be higher than the Fermi level of... 

Koper MTM, Heering HA. Comparison of Electrocatalysis and Bioelectrocatalysis, of Hydrogen and Oxygen Redox Reactions. In Wieckowski A, Norskov JK, editors. Fuel cell science. Hoboken, NJ Wiley-VCH 2010. Chapter 2. 

Oxygen reduction uccurs through the formation or peroxide intermediates. Vetier14 has reviewnd oxygen redox reactions at metal electrode surfaces, On platinum die current for calhedic reduction is... 

The energetic of the semiconductor must overlap those of the hydrogen and oxygen redox reactions. 

In fuel cells, well known catalyst is produced from carbon black-supported Pt particles (Pt/C) for hydrogen and oxygen redox reactions which occurs at anode and cathode but conventional Pt/C catalyst has low durability and can be easily poisoned by carbon monoxide. Electrospun Pt/ruthenium, Pt/rhodium, and Pt nanowires have been produced and compared with Pt/C showing better performance in a proton exchange membrane fuel cell (PEMFC). 

In the case of anode starvation, an anodic side reaction is required. Due to the low exchange current density of the oxygen redox reactions, even in the presence of a noble metal catalyst other side reactions (e.g. Pt dissolution or carbon corrosion) will take place in parallel to oxygen evolution. The potential of the anode will therefore rise significantly. 

Koper, M. T. M., and Heering, H. A. 2010. Comparison of electrocatalysis and hio-electrocatalysis of hydrogen and oxygen redox reactions, A. Wiecleowski and A. H. Heering, (Eds), Fuel Cell Science Theory, Fundamentals and Biocatalysis, pp. 71-110. Hoboken, NJ John Wiley Sons, Inc. 

Another approach for moving the oxygen redox reaction from the sohd surface to the solution phase is the use of an organic redox mediator (RM), in which the redox potentials of RM match those of the ORR and ORR, and the RM in both the reduced and oxidized states is soluble in the non-aqueous electrolyte. The RM catalyzes the ORR through a redox mechanism, which can be described by Eqs. 8 and 9, whereas the OER proceeds in the opposite direction. 

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