Transition electrocatalytic properties

Investigations of enzyme-catalyzed direct electron transfer introduce the basis for a future generation of electrocatalysts based on enzyme mimics. This avenue could offer new methods of synthesis for nonprecious metal electrocatalysts, based on nano-structured (for example, sol—gel-derived) molecular imprints from a biological catalyst (enzyme) with pronounced and, in some cases, unique electrocatalytic properties. Computational approaches to the study of transition state stabilization by biocatalysts has led to the concept of theozymes . " ... 

Phthalocyanine complexes are organic macrocycles with 18 7t-electrons, structurally resembling the naturally-occuring porphyrins complexes [1-3], Electrodes modified with transition metal (notably Fe, Co, Mn, Ni) phthalocyanine (MPc, Fig.l) complexes have continued to generate immense research interests because of their well-established electrocatalytic properties [3-6],... 

Ross,33 and Beard and Ross34 had also been interested in electrocatalytic properties of Pt-3d transition metal binary-alloys, with a view that stable intermetallics could be formed. It was also their view that the catalytic enhancement shown by Pt-V, Pt-Cr, and latterly Pt-Co was due to the surface roughening of the platinum crystallites caused by leaching of the non-platinum elements from the surface. In the case of the Pt-Co alloy, they believed that a more stable alloy is formed that protects against further alloy degradation. 

Many routes have been followed to use these organic conducting polymers as host matrices for the incorporation of various types of ionic or molecular species, which possessed promising electrocatalytic properties. These include metallic particles, metallic oxides, metal complexes, transition metal macrocycles, depending on the electrochemical reaction to be catalysed. 

The catalytic and electrocatalytic properties of the metaUoporphyrins are strongly influenced by the metal-ion, because the activation of a catalytic process generally depends on the coordination of the substrate to an active metal site. Consequently, its electronic and redox properties control the activity. On the other hand, these characteristics are more or less influenced by the nature of the transition metal complex bond to the peripheral pyridyl-substituents and its oxidation state. In this section, the catalytic properties of the peripherally metallated porphyrins will be presented starting with their behavior in solution and then as thin films. 

Fischer C, Alonsovante N, Fiechter S, Tributsch H (1995) Electrocatalytic properties of mixed transition metal tellurides (Chevrel-phases) for oxygen reduction. J Appl Electrochem 25(11) 1004-1008... 

Stamenkovic VR, Mun BS, Mayrhofer KJJ, Ross PN, Markovic NM (2006) liffect of surface composition on electronic structure, stability, and electrocatalytic properties of pt-transition metal alloys Pt-skin versus Pt-skeleton surfaces. J Am Chem Soc 128(27) 8813-8819... 

Chapters 7-12 focus on the electrocatalysis of carbon-based non-precious metal catalysts. The unique properties and fuel cell applications of various carbon based catalysts are intensively discussed in these chapters. Chapter 7 summarizes the fundamental studies on the electrocatalytic properties of metallomacrocyclic and other non-macrocyclic complexes. Chapter 8 and 9 review the progress made in the past 5 years of pyrolyzed carbon-supported nitrogen-coordinated transition metal complexes. Chapter 10 gives a comprehensive discussion on the role of transitional metals in the ORR electrocatalysts in acidic medium. Chapter 11 introduces modeling tools such as density functional theory (DPT) and ah initio molecular dynamics (AIMD) simulation for chemical reaction studies. It also presents a theoretical point of view of the ORR mechanisms on Pt-based catalysts, non-Pt metal catalysts, and non-precious metal catalysts. Chapter 12 presents an overview on recent progresses in the development of carbon-based metal-free ORR electrocatalysts, as well as the correlation between catalyst structure and their activities. 

Chapter 13 and 14 summarize the development of transitional metal oxides and transition metal chalcogenides for ORR, respectively. Chapter 15 is the only chapter in this book dedicated to the ORR catalysis of alkaline fuel cells. Electrocatalytic properties of various non-Pt catalysts including Ag, Pd, transition metal macrocycles, metal oxides, and multifunctional materials are presented. Fundamental issues related to the design of low-cost, high-performance electrocatalysts for alkaline fuel cells are discussed. Chapter 16 and 17 review the recent advances on the study of ORR on Au and Pd-based catalysts, respectively. 

Mechanisms of electrochemical reactions of different systems, including transition metal complexes, were examined with a special attention paid to double layer effects and problems of generation and decay of intermediates which arise in such reactions. Electrodes modified with thin films of transition metal hexacyanoferrates and conducting polymers were investigated, also solid state electrochemistry in the absence of external supporting electrolyte were developed. Charge propagation rate in such mixed-valent solid systems and their electrocatalytic properties were studied. 

In a previous review [4], we focused on the electrocatalytic properties of well-characterized supermolecules, generated by the coordination of transition metal complexes, such as ruthenium polypyridines and triangular ruthenium acetate... 

Polyoxometallates (POMs) are heteropolyanions exhibiting electrocatalytic properties, which are existing in the form of Keggin-type (XMi204o" ), Dawson-type (X2Mig062" ), mixed-addenda, or transition metal-substituted structures. Eol-lowing some pioneering works on POM-modified CPEs, the most widely... 

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