Nanoparticles electrocatalysis

Electrical current is generated at highly dispersed catalyst nanoparticles. Atomistic surface structures of catalyst particles determine their specific activities. Detailed models in nanoparticle electrocatalysis have to distinguish the contributions of distinct surface sites to the relevant electrocatalytic... 

Moghaddam RB, Pickup PG (2011) Support effects on the oxidation of formic acid at Pd nanoparticles. Electrocatalysis 2 159-162... 

Knupp SL, Vukmirovic MB, Haidar P, Herron JA, Mavrikakis M, Adzic RR (2010) Platinum monolayer electrocatalysts for O2 reduction Pt monolayer on carbon-supported Pdir nanoparticles. Electrocatalysis... 

The consideration of effects included in and Fcl suggest that improvements in structure and function of catalyst layers should be pursued in three areas (1) nanoparticle electrocatalysis (interplay of and r p), (2) statistical utilization of the catalyst (Pstat), and (3) mixed transport in composite media (fagg). These areas encompass a hierarchy of kinetic and transport processes that span many scales. 

In nanoparticle electrocatalysis, the area that Michael entered just some time ago in Munich, he and his coworkers rationalized the sensitivity of electrocatalytic processes to the stmcture of nanoparticles and interfaces. Studies of catalytic effects of metal oxide support materials revealed intriguing electronic structure effects on thin films of Pt, metal oxides, and graphene. In the realm of nanoparticle dissolution and degradation modeling, Michael s group has developed a comprehensive theory of Pt mass balance in catalyst layers. This theory relates surface tension, surface oxidation state, and dissolution kinetics of Pt. 

Since 1976 until present time Toshima-t5q)e nanocolloids always had a major impact on catalysis and electrocatalysis at nanoparticle surfaces [47,210-213,398-407]. The main advantages of these products lie in the efficient control of the inner structure and morphology especially of bimetallic and even multimetallic catalyst systems. 

T. Teranishi, N. Toshima, in A. Woekowski, E. R. Savinova, C. G. Vayenas (eds.). Catalysis and Electrocatalysis at Nanoparticle Surfaces, Marcel Dekker, New York, 2003. 

Another electro-oxidation example catalyzed by bimetallic nanoparticles was reported by D Souza and Sam-path [206]. They prepared Pd-core/Pt-shell bimetallic nanoparticles in a single step in the form of sols, gels, and monoliths, using organically modified silicates, and demonstrated electrocatalysis of ascorbic acid oxidation. Steady-state response of Pd/Pt bimetallic nanoparticles-modified glassy-carbon electrode for ascorbic acid oxidation was rather fast, of the order of a few tens of seconds, and the linearity was observed between the electric current and the concentration of ascorbic acid. 

Koper MTM, van Santen RA, Neurock M. 2003. Theory and modeling of catalytic and electro-catalytic reactions. In Savinova ER, Vayenas CG, Wieckowski A, eds. Catalysis and Electrocatalysis at Nanoparticle Surfaces. New York Marcel Dekker. pp. 1-34. 

It has been often stressed that low eoordinated atoms (defeets, steps, and kink sites) play an important role in surfaee ehemistry. The existenee of dangling bonds makes steps and kinks espeeially reaetive, favoring the adsorption of intermediate species on these sites. Moreover, smdies of single-crystal surfaces with a eomplex geometry have been demonstrated very valuable to link the gap between fundamental studies of the basal planes [Pt( 111), Pt( 100), and Pt(l 10)] and applied studies of nanoparticle eatalysts and polycrystalline materials. In this context, it is relevant to mention results obtained with adatom-modified Pt stepped surfaces, prior to discussing the effect of adatom modification on electrocatalysis. 

Size Effects in Electrocatalysis of Fuel Cell Reactions on Supported Metal Nanoparticles... 

Summing up this section, we would like to note that understanding size effects in electrocatalysis requires the application of appropriate model systems that on the one hand represent the intrinsic properties of supported metal nanoparticles, such as small size and interaction with their support, and on the other allow straightforward separation between kinetic, ohmic, and mass transport (internal and external) losses and control of readsorption effects. This requirement is met, for example, by metal particles and nanoparticle arrays on flat nonporous supports. Their investigation allows unambiguous access to reaction kinetics and control of catalyst structure. However, in order to understand how catalysts will behave in the fuel cell environment, these studies must be complemented with GDE and MEA tests to account for the presence of aqueous electrolyte in model experiments. 

As the reader might have noticed, many conclusions in electrocatalysis are based on results obtained with electrochemical techniques. In situ characterization of nanoparticles with imaging and spectroscopic methods, which is performed in a number of laboratories, is invaluable for the understanding of PSEs. Identification of the types of adsorption sites on supported metal nanoparticles, as well as determination of the influence of particle size on the adsorption isotherms for oxygen, hydrogen, and anions, are required for further understanding of the fundamentals of electrocatalysis. 

Cherstiouk OV, Simonov PA, Savinova ER. 2003a. Model approach to evaluate particle size effects in electrocatalysis Preparation and properties of Pt nanoparticles supported on GC and HOPG. Electrochim Acta 48 3851-3860. 

Guerin S, Hayden BE, Pletcher D, Rendall ME, Suchsland J-P, WiUiams LJ. 2006b. Combinatorial approach to the study of particle size effects in electrocatalysis synthesis of supported gold nanoparticles. J Comb Chem 8 791-798. 

Pronkin SN, Tsirlina GA, Petrii OA, Vassiliev SY. 2001. Nanoparticles of Pt hydrosol immobilized on Au support An approach to the study of structural effects in electrocatalysis. Electrochim Acta 46 2343-2351. 

Solla-Gullon J, Vidal-Iglesias FJ, Rodriguez P, Herrero E, Feliu JM, Aldaz A. 2005. Shape-dependent electrocatalysis CO monolayer oxidation at platinum nanoparticles. Paper presented at Meeting ECS, May 15-20, 2005, Quebec City. 

Figure 17.11 Schematic representation of an approach for achieving efficient electrocatalysis of glucose oxidation by glucose dehydrogenase on Au nanoparticles tethered on an Au electrode. The nanoparticles are modified with a PQQ-capped linker that interacts with the unoccupied PQQ site of cofactor-deficient glucose dehydrogenase [Zayats et al., 2005].

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