Electrocatalyst spillover

Carbon is the usual support because of its high conductivity and relative high resistance to corrosion synergetic effects such as electronic spillover is possible in supported electrocatalysts. 

Related to these matters has been the question whether two-component electrode metals (dual-site model) could lead to an electrocatalyst surface that exhibited catalytic properties better than either of its components. Qualitative ideas about electron spillover between one component and another at microcrystal grain boundaries, or transfer of the chemisorbed intermediate from one site to another, could suggest the possibility of such an effect. However, a quantitative theoretical analysis of this question by Parsons (149), based on his treatment of chemisorption effects at single metals (23) having various AG ,, h values, showed that, for practical applications, almost no... 

Lambert reviews the role of alkali additives on metal films and nanoparticles in electrochemical and chemical behavior modihcations. Metal-support interactions is the subject of the chapter by Arico and coauthors for applications in low temperature fuel cell electrocatalysts, and Haruta and Tsubota look at the structure and size effect of supported noble metal catalysts in low temperature CO oxidation. Promotion of catalytic activity and the importance of spillover are discussed by Vayenas and coworkers in a very interesting chapter, followed by Verykios s examination of support effects and catalytic performance of nanoparticles. In situ infrared spectroscopy studies of platinum group metals at the electrode-electrolyte interface are reviewed by Sun. Watanabe discusses the design of electrocatalysts for fuel cells, and Coq and Figueras address the question of particle size and support effects on catalytic properties of metallic and bimetallic catalysts. 

The significance of hydrogen spillover synergism is well established for Pt-doped bronze electrocatalysts, involving the following steps ... 

In the previous example the supported metal oxide onto which the metal precursor was adsorbed did not reduce which will be the case for many promoted systems. In many systems, however, the supported metal oxide will reduce, especially through hydrogen spillover, and a bimetallic catalyst can be synthesized. The idea is illustrated in Figure 3.11a for the Pd/Co/C electrocatalyst system. The idea will be to adsorb Pd complexes onto a well-dispersed, carbon-supported C03O4 phase, and reduce to get bimetallic Pd/Co particles that are perhaps core-shell in morphology. 

An important factor affecting the performance of DMFCs is the kinetics of catalyst. Platinum (Pt/C) is the most effective catalyst for oxygen reduction reaction but it is not selective towards ORR in presence of methanol. The addition of yttrium to Pt increases the ORR activity and are promising ORR electrocatalyst [207]. Carbon supported PtY(OH)3 hybrid catalyst are developed with dynamic spillover of metal oxide [208]. Recently, catalyst for DMFC Pt Pd/C NP was prepared by the galvanic displacement reaction between Pt and Pd. A simple synthesis strategy was followed to prepare carbon based [209] and carbon-supported Pd nanostructure [190]. A higher methanol tolerance of Pt Pd/C with less Pt content than Pt/C suggests that it is potential alternative cathode electrocatalyst for DMFCs [190]. 

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