Electrocatalysts design

Zhang, J. et al., Platinum and mixed platinum-metal monolayer fuel cell electrocatalysts design, activity and long-term performance stability, ECS Trans., 3, 31, 2006. 

From the electrochemical engineering point of view, the electrocatalyst design depends on the purpose of the electrochemical reactor, gas electrosynthesis, organic synthesis, batteries or supercapacitors, metal electrodeposition, and the fuel cells. 

ELECTROCATALYST DESIGN AND HYDRODYNAMIC CONDITIONS 14.2.1 Electrocatalyst Failure Factors... 

Siahrostami, S., Verdaguer-Casadevall, A., Karamad, M., Deiana, D., Malacrida, R, Wickman, B., Rossmeisl, J. (2013). Enabhng direct H2O2 production through rational electrocatalyst design. Aa/nre Afafen a/j, 12(12), 1137—1143. 

ELECTROCATALYST DESIGN IN PROTON EXCHANGE MEMBRANE FUEL CELLS FOR AUTOMOTIVE APPLICATION... 

The change in the electronic properties of Ru particles upon modification with Se was investigated recently by electrochemical nuclear magnetic resonance (EC-NMR) and XPS [28]. In this work, it was established for the first time that Se, which is a p-type semiconductor in elemental form, becomes metallic when interacting with Ru, due to charge transfer from Ru to Se. On the basis of this and previous results, the authors emphasized that the combination of two or more elements to induce electronic alterations on a major catalytic component, as exemplified by Se addition on Ru, is quite a promising method to design stable and potent fuel cell electrocatalysts. 

Appreciable interest was stirred by the sucessful use of nonmetallic catalysts such as oxides and organic metal complexes in electrochemical reactions. From 1968 on, work on the development of electrocatalysts on the basis of the mixed oxides of titanium and ruthenium led to the fabrication of active, low-wear electrodes for anodic chlorine evolution which under the designation dimensionally stable anodes (DSA) became a workhorse of the chlorine industry. 

Adsorbed CO on a metal surface is one of the simplest adsorbates and has attracted significant interest within the areas of fundamental surface science, catalysis, and electrochemistry. An understanding of the oxidation mechanism of adsorbed CO is important to design and develop electrocatalysts for fuel cells [69-73] and the surface dynamics of adsorbed CO on electrode surfaces in electrolyte solutions is, therefore, very important. 

Significant (and even spectacular) results were contributed by the group of Norskov to the field of electrocatalysis [102-105]. Theoretical calculations led to the design of novel nanoparticulate anode catalysts for proton exchange membrane fuel cells (PEMFC) which are composed of trimetallic systems where which PtRu is alloyed with a third, non-noble metal such as Co, Ni, or W. Remarkably, the activity trends observed experimentally when using Pt-, PtRu-, PtRuNi-, and PtRuCo electrocatalysts corresponded exactly with the theoretical predictions (cf. Figure 5(a) and (b)) [102]. 

Markovic NM, Ross PN. 2000. Electrocatalysts by design From the tailored surface to a commercial catalyst. Electrochim Acta 45 4101-4115. 

The alcohol tolerance of O2 reduction by bilirubin oxidase means that membraneless designs should be possible provided that the enzymes and mediators (if required) are immoblized at the electrodes. Minteer and co-workers have made use of NAD -dependent alcohol dehydrogenase enzymes trapped within a tetraaUcylammonium ion-exchanged Nafion film incorporating NAD+/NADH for oxidation of methanol or ethanol [Akers et al., 2005 Topcagic and Minteer, 2006]. The polymer is coated onto an electrode modified with polymethylene green, which acts as an electrocatalyst... 

The prevalence of the heme in O2 metabolism and the discovery in the 1960s that metallophthalocyanines adsorbed on graphite catalyze four-electron reduction of O2 have prompted intense interest in metaUoporphyrins as molecular electrocatalysts for the ORR. The technological motivation behind this work is the desire for a Pt-ffee cathodic catalyst for low temperature fuel cells. To date, three types of metaUoporphyrins have attracted most attention (i) simple porphyrins that are accessible within one or two steps and are typically available commercially (ii) cofacial porphyrins in which two porphyrin macrocycles are confined in an approximately stacked (face-to-face) geometry and (iii) biomimetic catalysts, which are highly elaborate porphyrins designed to reproduce the stereoelectronic properties of the 02-reducing site of cytochrome oxidase. 

Only a limited number of true metal complex electrocatalysts have been proposed for proton reduction due to the difficulty inherent in the bielectronic nature of this reaction. It is obvious that the design of such electrocatalysts must take into account the lowering of the overpotential for proton reduction, the stability of the catalytic system, and the regeneration of the starting complex. 

Synchotron based techniques, such as surface X-ray scattering (SXS) and X-ray absorption spectroscopy (XAS), have found increased use in characterization of electrocatalysts during electrochemical reactions.37 These techniques, which can be used for characterization of surface structures, require intricate cell designs that can provide realistic electrochemical conditions while acquiring spectra. Several examples of the use of XAS and EXAFS in non-precious metal cathode catalysts can be found in the literature.38 2... 

Platinum-free electrocatalysts for fuel cells could be designed when Pd on carbon electrocatalysts promoted with nanocrystal oxide particles like C03O4, Mn30 and NiO, were used [62], In terms of activity and poison tolerance, the latter were significantly superior. 

Y. D. Jin, Y. Shen, and S. J. Dong, Electrochemical design of ultrathin platinum-coated gold nanoparticle monolayer films as a novel nanostructured electrocatalyst for oxygen reduction, J. Phys. Chem. B 108, 8142-8147 (2004). 

The electrolyte in the AFC is concentrated (85 wt%) KOH in cells designed for operation at high temperature ( 260°C), or less concentrated (35-50 wt%) KOH for lower temperature (<120°C) operation. The electrolyte is retained in a matrix (usually asbestos), and a wide range of electrocatalysts can be used (e.g., Ni, Ag, metal oxides, spinels and noble metals). 

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