Oxygen reduction reaction metal-polymer electrolyte

Jaouen F, Proietti E, Lefevre M, Chenitz R, Dodelet J-P, Wu G, Chimg HT, Johnston CM, Zelenay P (2011) Recent advances in non-precious metal catalysis for oxygen-reduction reaction in polymer electrolyte fuel cells. En gy Environ Sci 4(1) 114-130... 

Currently used electrode-catalysts (anode and cathode) consist of an assembly of metallic nanoparticles usually deposited on an electronic conducting substrate and embedded in a hydrated membrane [10, 11], which is the polymer electrolyte proton-conductive material (Figure 17.1). What differs between cathode and anode is the catalyst material, and also the significantly slow kinetics of the cathode oxygen reduction reaction compared to that of the anode hydrogen oxidation reaction. For this reason, several... 

Platinum has a myriad of practical uses, especially in the field of electrochemistry where it is used as a catalyst and as a reference electrode. In particular, platinum is the most active known pure metal for the oxygen reduction reaction (ORR) in which O2 is split and combined with protons to form H2O. This is an important step in low-temperature fuel cells (polymer electrolyte fuel cells, direct methanol fuel cells, etc.) as it often is what limits the total fuel cell efficiency. Furthermore, platinum is rather expensive with the materials cost of its use in fuel cells being roughly half of the total fuel cell cost. Consequently, a great deal of effort is made in order to optimize its use. 

Kobayashi M, Niwa H, Harada Y, Horiba K, Oshima M, Ofuchi H, Terakura K, Ikeda T, Koshigoe Y, Ozaki JI, Miyata S, Ueda S, Yamashita Y, Yosikawa H, Kobayashi K (2011) Role of residual transition metal atoms in oxygen reduction reaction in cobalt phthalocyanine-based carbon cathode catalysts for polymer electrolyte fuel cell. J Power Sources 196 8346-8351... 

Fuel Cells, Non-Precious Metal Catalysts for Oxygen Reduction Reaction Platinum-Based Cathode Catalysts for Polymer Electrolyte Fuel Cells... 

Other approaches have focused upon using non-precious metals and their oxides as alternatives to the platinum catalysts. For example, the mixed oxide catalysts of the binary and ternary alloys of noble metals and transition metals have been investigated for the oxygen evolution reaction in solid polymer electrolyte water electrolyzers. Binary, ternary, and quaternary platinum alloys with base metals of Cu, Ni, and Co have been used as electrocatalysts in liquid acid electrolyte cells. It was also reported that a R-Cu-Cr alloy displayed better activity to oxygen reduction than R and Pt-Cr in liquid electrolyte.The enhanced electrocatalytic activity of these types of alloys has been attributed to various factors, including the decrease of the nearest neighbor distance of platinum,the formation of Raney type... 

This value is close to the electrode potential of the dry passivated iron surface. Obviously, the activation which has happened at the defect after the addition of the electrolyte does not take place at the intact interface, despite the fact that oxygen and water will permeate through the coating at a high rate (Nguyen et al., 1991, 1994 Stratmann et al., 1994 Fes-er and Stratmann, 1990). From an electrochemical point of view, this must be due to the inhibition of the metal dissolution reaction at the passivated sub-strate/polymer interface, which does not allow any anodic current and therefore shifts the electrode potential anodically until the rate of oxygen reduction is also reduced significantly (Stratmann, 1994). 

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