Palladium-based electrocatalysts

Bianchini, C. and Shen, P.K. (2009) Palladium-based electrocatalysts for alcohol oxidation in half cells and in direct alcohol fuel cells. Chemical Reviews,... 

Palladium-Based Electrocatalysts for Oxygen Reduction Reaction... 

Shao M (2011) Palladium-based electrocatalysts fin hydrogen oxidation and oxygen reduction reactions. J Power Sources 196(5) 2433—2444... 

Bae, S.J., Kim, S.-J., Park, J.I., Lee, J.-H., Cho, H., and Park, J.-Y. (2010) Lifetime prediction through accelerated degradation testing of membrane electrode assemblies in direct methanol fuel cells. Int.J. Hydrogen Energy, 35, 9166-9176. Shao, M. (2011) Palladium-based electrocatalysts for hydrogen oxidation and oxygen reduction reactions. J. Power Sources, 196, 2433-2444. 

In a recent review paper by Shao (2011) the author mentions that because of limited resources and high cost, platinum electrocatalysts, used in many low-temperature fuel cells, hinder the commercialization of fuel cell power plants. Recent efforts have focused on the discovery of palladium-based electrocatalysts with no or little platinum. The paper overviews progress in electrocatalysis by palladium-based materials for the reaction of hydrogen oxidation as well for the reaction of oxygen reduction (see the next section). 

To improve the electrocatalytic activity of platinum and palladium, the ethanol oxidation on different metal adatom-modified, alloyed, and oxide-promoted Pt- and Pd-based electrocatalysts has been investigated in alkaline media. Firstly, El-Shafei et al. [76] studied the electrocatalytic effect of some metal adatoms (Pb, Tl, Cd) on ethanol oxidation at a Pt electrode in alkaline medium. All three metal adatoms, particularly Pb and Tl, improved the EOR activity of ft. More recently, Pt-Ni nanoparticles, deposited on carbon nanofiber (CNE) network by an electrochemical deposition method at various cycle numbers such as 40, 60, and 80, have been tested as catalysts for ethanol oxidadmi in alkaline medium [77]. The Pt-Ni alloying nature and Ni to ft atomic ratio increased with increasing of cycle number. The performance of PtNi80/CNF for the ethanol electrooxidation was better than that of the pure Pt40/CNF, PtNi40/CNF, and PtNi60/CNF. 

Palladium is more abundant in nature and sells at half the current market price of platinum. Unlike Pt, the Pd-based electrocatalysts are more active towards the oxidation of a plethora of substrates in alkaline media. The high activity of Pd in alkaline media is advantageous considering that non-noble metals are sufficiently stable in alkaline for electrochemical applications. Importantly, it is believed that the integration of Pd with non-noble metals (as bimetallic or ternary catalysts) can remarkably reduce the cost of the membrane electrode assemblies (MEAs) and boost the widespread application or commercialization of DAFCs [1]. Palladium has proved to be a better catalyst for alcohol electrooxidation in alkaline electrolytes than Pt [2]. Palladium activity towards the electrooxidation of low-molecular weight alcohols can be enhanced by the presence of a second or third metal, either alloyed or in the oxide form [3]. 

Wang X, Kariuki N, Niyogi S, Smith MC, Myers DJ, Hofmann T, Zhang Y, Bar M, Heske C (2008) Bimetallic palladium-base metal nanoparticle oxygen reduction electrocatalysts. ECS Trans 16 109-119... 

Tarasevich MR, Zhutaeva GV, Bogdanovskaya VA, Radina MV, Ehrenburg MR, Chalykh AE. 2007. Oxygen kinetics and mechanism at electrocatalysts on the base of palladium-iron system. Electrochim Acta 52 5108-5118. 

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