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The adsorption of 4-aminobenzenethiol (4-ABT) on Ag and Pt nanoparticles is studied by spectroelectrochemical means (cyclic voltammetry, Surface-Enhanced Raman Spectroscopy (SERS) and Surface-Enhanced Infrared Reflection Absorption Spectroscopy (SEIRAS). Similar SERS spectra are obtained when 4-ABT is adsorbed on platinum and silver nanostructured substrates. In addition, unless a low power density of the laser is used, these spectra show, both under open circuit conditions and when applying electrode potentials above -0.50 V, bands not observed in the normal Raman spectrum of 4-ABT. These bands disappear when the electrode potential is shifted to more negative values. Conversely, the SEIRA spectra of 4-ABT adsorbed on Ag do not show any significant change with the electrode potential, which indicates that there are not new species electrochemically formed in the range of potentials considered, which include some anodic and cathodic processes as shown in the corresponding cyclic voltammograms. In this regard, SERS measurements put in evidence the time dependence of the spectra obtained at potentials above -0.50 V just after switching on the laser suggesting the formation of new species, probably dimercaptoazobenzene (4-4’-DMAB), formed by a photochemical process of the adsorbed 4-ABT. Financial support from Ministerio de Ciencia e Innovación (projects CTQ2010-16271, CTQ2009-13142, and Fondos Feder), Generalitat Valenciana (Prometeo/2009/045 and ACOMP/2011/200), and University of Alicante is greatly acknowledged.

Using the spontaneous deposition method (W. Chrzanowski and A. Wieckowski, Langmuir13, 5974 (1997)), platinum nanoparticles were decorated with ruthenium to obtain a Pt/Ru catalyst with a packing density of up to 0.65 Ru atoms per Pt surface atom. The activity of this catalyst toward methanol electrooxidation was tested at electrode potentials of interest for fuel cells. The catalyst activity maximizes at ruthenium packing density 0.4–0.5, and the catalyst is twice as active (displays higher current densities normalized to real surface area) as the commercial 50 : 50 Pt/Ru alloy catalyst. Hydrogen adsorption on the decorated Pt/Ru and Pt/Ru alloy surfaces is also reported.

A new process to clean nanoparticles of platinum obtained by a water-in-oil (W/O) microemulsion without loss of crystalline structure was studied. Polyethyleneglycol–dodecylether (BRIJ®30) was the surfactant used for the preparation of the platinum particles. Pt(111), Pt(110), Pt(100) and polyoriented platinum electrodes were used to check the effectiveness of this new procedure. Preliminary results obtained with nanoparticles of platinum are also presented. The voltammetric profiles of platinum particles show the adsorption states associated with (110), (100) and (111) domains. The ratio Pt SURF /Pt TOT was found to be 0.1 for an upper potential limit of 1 V and 0.12 for an upper potential limit of 1.5 V.

Silver–platinum core–shell (Ag@Pt) nanoparticles have been synthesized using various methods. In the case of Ag@Pt nanoparticles synthesized by the standard method based on the galvanic replacement reaction between Ag seeds and PtCl42−, transmission electron microscopy micrographs revealed well visible core–shell structure. However, electrochemical experiments showed that relatively large amount of silver can be easily stripped off from such nanoparticles. Significant improvement on the integrity of the deposited platinum shell can be achieved when nanoparticles are synthesized by the seeded growth reaction including reduction of PtCl42− with ascorbic acid at room temperature. To obtain pinhole-free platinum layers (where Ag oxidation is not observed) relatively large amount of platinum must be deposited. For example, to cover 11 nm Ag seeds, the number of moles of platinum in the formed Ag@Pt nanoparticles must be at least equal to the number of moles of Ag. It was also found that a similar seeded growth reaction may be used to form pinhole-free Au@Pt nanoparticles. The electrochemical behaviour of those two systems (Ag@Pt and Au@Pt nanoparticles) towards CO stripping was rather different. While the CO-stripping on Au@Pt occurred at typical potentials and without a significant reconstruction of the original surface, CO stripping voltammograms on Ag@Pt were very unusual and exhibited both exceptionally strong binding of CO to the surface, and such a reconstruction of the surface that silver atoms were no longer compactly covered by platinum. This project was financed from the funds of the National Science Centre (Poland) allocated on the basis of the decision number DEC-2011/01/B/ST4/00581 and co-financed by the European Regional Development Fund within the Innovative Economy Operational Programme 2007–2013 No POIG.02.01-00-14-032/08. S.W. is thankful for the support from the Foundation for Polish Science MPD Programme co-financed by the EU European Regional Development Fund.

The increasing number of applications for shape-controlled metal nanoparticles (NPs) has led to the need for easy, cheap, and scalable methodologies. We report the synthesis of (100) preferentially oriented Pt NPs, with a particle size of 9 nm, by using a water-in-oil microemulsion method. The specific surface structure of the NPs is induced by the presence of H2SO4 in the water phase of the microemulsion. Interestingly, the results reported herein show how increasing amounts of H2SO4 lead to the formation of Pt NPs containing a larger amount of (100) sites on their surface. This preferential surface orientation is confirmed electrochemically by using the so-called hydrogen adsorption/desorption process. In addition, transmission electron microscopy measurements confirm the presence of cubic-like Pt NPs. Finally, the electrocatalytic properties of the Pt NPs are evaluated towards ammonia and CO electro-oxidations, which are (100) structure-sensitive reactions. This work has been financially supported by the MCINN-FEDER (Spain) (project CTQ 2010-16271), Generalitat Valenciana (project PROMETEO/2009/045) and in part by NASA-URC Grant No. NNX10AQ17A and NSF-NSEC Center for Hierarchical Manufactur-ing Grant No. CHM-CMMI-0531171. R. M-R is grateful to the Becas Iberoamérica, Santander Universidades-España 2012 and PR-LSAMP Bridge to Doctorate Fellowship programs.

Thallium modified shape-controlled Pt nanoparticles were prepared and their electrocatalytic activity towards formic acid electrooxidation was evaluated in 0.5 M sulfuric acid. The electrochemical and in situ FTIR spectroscopic results show a remarkable improvement in the electrocatalytic activity, especially in the low potential region (around 0.1–0.2 V vs. RHE). Cubic Pt nanoparticles modified with Tl were found to be more active than the octahedral Pt ones in the entire range of Tl coverages and potential windows. In situ FTIR spectra indicate that the promotional effect produced by Tl results in the inhibition of the poisoning step leading to COads, thus improving the onset potential for the complete formic acid oxidation to CO2. Chronoamperometric experiments were also performed at 0.2 V to evaluate the stability of the electrocatalysts at constant potential. Finally, experiments with different concentrations of formic acid (0.05–1 M) were also carried out. In all cases, Tl-modified cubic Pt nanoparticles result to be the most active. All these facts reinforce the importance of controlling the surface structure of the electrocatalysts to optimize their electrocatalytic properties. This work has been financially supported by the MICINN (Spain) (project CTQ2010-16271) and Generalitat Valenciana (project PROMETEO/2009/045 – FEDER).

The influence of the electrolyte pH on formic acid (HCOOH) electrooxidation is investigated on both polycrystalline Pt and Au electrodes and on single-crystalline Au electrodes in perchloric and sulfuric acid-based electrolytes. On Au electrodes, the potentiodynamic oxidation currents are found to depend, in a nonlinear way, on the electrolyte pH in a bell-shaped relation, with a maximum of the catalytic activity at the pKa of HCOOH. On polycrystalline Pt electrodes, this feature is not observed; the catalytic activity increases steadily with increasing pH up to a pH value of approximately 5, which is followed by a plateau until pH 10, in contrast with recent observations [J. Joo, T. Uchida, A. Cuesta, M. T. M. Koper, M. Osawa, J. Amer. Chem. Soc.­ 2013, 135, 9991–9994]. In addition, for Au surfaces, the reaction is only weakly influenced by the electrode surface structure, whereas for Pt, structural effects are known to be considerable. Anion effects, in contrast, are much stronger for the reaction on Au electrodes compared to Pt electrodes. Also, it is shown that Pt-group-metal-free Au electrodes do not oxidize molecular hydrogen under reaction conditions. The results are discussed in relation to findings in previous mechanistic studies. Most importantly, the activity on both electrodes is closely correlated with the concentration of HCOO−, and for Au correlates with both HCOO− and HCOOH concentrations. Based on these results, a number of mechanistic proposals put forward in earlier studies must be discarded, and examples for mechanisms compatible with these results are discussed. This work was supported by the Ministerio de Economía y Competitividad (MINECO) (Spain) (project EUI2009–04176) and by the Deutsche Forschungsgemeinschaft (BE 1201/17–1).

In this work, the behavior of the CO electro-oxidation reaction on shape-controlled Pt nanoparticles in alkaline medium was examined in order to understand the effect of the surface structure on this reaction. A series of experiments using Pt nanoparticles of different surface structures/shapes was used and the results obtained were compared with the previous knowledge gained from stepped platinum single crystal electrodes. Independently of the preferential orientation of the nanoparticles, the CO oxidation voltammetry exhibits two main peaks: one at ca. 0.56–0.59 V and the second one at 0.66–0.67 V, being the intensity of the peaks dependent on the shape of the nanoparticle. These two peaks have been assigned to the oxidation of CO on the (1 1 1) terraces and on the rest of the sites, respectively. The appearance of two differentiated peaks reveals that these (1 1 1) terraces and the rest of the sites on the nanoparticle surface behave independently of the presence of the other type of sites, that is, they are not connected. The results are discussed considering the effects of the surface mobility of CO and of the OH adsorption properties on the different sites in the oxidation peaks. Farias, M.J.S. would like to thanks CNPq, Brazil, for financial support for his postdoctoral stay at Universidad de Alicante. This work has been financially supported by the MICINN (Spain) (project CTQ2010-16271) and Generalitat Valenciana (project PROMETEO/2009/045, FEDER).

If you ask undergraduate students of Chemistry “Do you understand the electrochemical Nernst equation [1]?”, a high percentage of them will answer “Of course, we do! It is the equation that relates the activity of the species taking part in an electrochemical equilibrium to its electrode potential!” The next question: “So, would you be able to calculate how the electrode potential of the reaction Aþ Hþ þ e ! D ð1Þ

A new method for in situ surface characterization of preferentially oriented platinum nanoparticles is presented. The method is based on the use of structure-sensitive surface reactions such as the redox behavior of underpotential and spontaneous deposition of adatoms. Examples of its use for surface characterization of Pt nanoparticles synthesized by different methods are given. The method has been also employed to rationalize the different behavior of these Pt nanoparticles for the ammonia electro-oxidation in a basic medium.

This chapter reviews the recent advances on the study of the oxygen reduction reaction (ORR) on gold electrodes. The initial part is devoted to the study of the reaction on single-crystal electrodes to determine the effect of the surface structure on the reactivity of gold electrodes for this reaction. The best reactivity is found for the Au(100) electrode in alkaline medium. For the nanoparticle electrodes, the reactivity for this reaction depends on two different effects: size and surface structure effects. Regarding the size effects, the different studies found in the literature do not agree on whether the size of the nanoparticles has a significant impact on the reactivity for the ORR. This disagreement between different authors is probably due to the lack of control of the surface structure of the nanoparticles. On the other hand, significant effects are found when the surface of the nanoparticle is changed. In general, the reactivity in alkaline media increases as the fraction of {100} domains on the surface increases. In some cases, the reactivity of gold in alkaline medium is similar to that measured for platinum electrodes.

The electrocatalytic properties of palladium nanocubes towards the electrochemical oxidation of formic acid were studied in H(2)SO(4) and HClO(4) solutions and compared with those of spherical Pd nanoparticles. The spherical and cubic Pd nanoparticles were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The intrinsic electrocatalytic properties of both nanoparticles were shown to be strongly dependent on the amount of metal deposited on the gold substrate. Thus, to properly compare the activity of both systems (spheres and nanocubes), the amount of sample has to be optimized to avoid problems due to a lower diffusion flux of reactants in the internal parts of the catalyst layer resulting in a lower apparent activity. Under the optimized conditions, the activity of the spheres and nanocubes was very similar between 0.1 and 0.35 V. From this potential value, the activity of the Pd nanocubes was remarkably higher. This enhanced electrocatalytic activity was attributed to the prevalence of Pd(100) facets in agreement with previous studies with Pd single crystal electrodes. The effect of HSO(4)(-)/SO(4)(2-) desorption-adsorption was also evaluated. The activity found in HClO(4) was significantly higher than that obtained in H(2)SO(4) in the whole potential range.

The voltammetric profile of preferentially shaped platinum nanoparticles has been used to analyze the different sites present on the surface. For the first time, this analysis has been made in NaOH solutions and revisited in sulfuric and perchloric acid media. The comparison with the voltammetric profiles of the model surfaces, that is, single-crystal electrodes, allows assigning the different signals appearing in the voltammograms of the nanoparticle to specific sites on the surface. A good correlation between the shape of the nanoparticle determined by TEM and the voltammetric profile is obtained. For the nanoparticles characterized in alkaline media, the adsorbed species on the surface have been characterized, and three major regions can be identified. Below 0.2 V, the major contribution is due to hydrogen adsorption, whereas above 0.6 V, adsorbed OH is the main species on the surface. Between those values, the signals are due to the competitive adsorption/desorption process of OH/H. New criteria for determining the active area in NaOH solutions has been proposed. In this medium, the total charge density measured between 0.06 and 0.90 V stands for 390 μC cm–2. The areas measured are in perfect agreement with those measured in acid media. Once the nanoparticles have been characterized, the behavior of the nanoparticles toward CO oxidation is analyzed and compared with that observed for single-crystal electrodes. This work has been financially supported by the MICINN (Spain) (Project CTQ2010-16271) and Generalitat Valenciana (Project PROMETEO/2009/045, -FEDER).

Carbon nanotubes have been proposed as advanced metal catalyst support for electrocatalysis. In this paper, Pt nanoparticles supported on single-walled carbon nanotubes (SWCNTs)-Pt, were prepared using a solid-state reaction between the SWCNTs and two different Pt precursors, bis(dibenzylideneacetone)platinum [Pt(DBA)2] or tri(dibenzylideneacetone)platinum [Pt(DBA)3]. TEM images of the samples show Pt nanoparticles with a particle size around 2.5 nm with a high degree of dispersion on the SWCNTs. A detailed electrochemical characterization of the surface of the samples including irreversibly adsorbed adatoms of Bi and Ge as probe reactions has been carried out. It has been stated that SWCNTs-Pt samples subjected to the classical electrochemical activation induce a serious sintering of the Pt nanoparticles., This work has been performed in the framework of projects BQU2003-03877 and BQU2003-4029 from MCyT (Spain), project MAT2002-04630-C02-01 from MEC (Spain) and projects GRUPOS03/126 and GRUPOS03/208 from GV (Spain).

In recent years palladium has proven to be a good alternative to platinum in low-temperature fuel cell cathode catalysts.1 The electrocatalytic activity of Pd catalysts toward the oxygen reduction reaction (ORR) can be improved by preparing shape-controlled nanoparticles.2 The aim of this study was to investigate the electrocatalytic activity of carbon-supported Pd nanocubes of different size and varied metal loading toward the ORR. CTAB or PVP were used as capping agents to prepare the Pd nanocubes of different sizes. The morphology of Pd/C catalyst was evaluated using transmission electron microscopy, which showed that the particles are cube shaped and their size depends on the synthesis method. The thermogravimetric method was used to determine the Pd loading on carbon. The nominal Pd contents of the prepared catalysts were 5, 20 and 50 wt% and the measured content deviated only slightly. Electrochemical experiments were carried out in acid and alkaline solutions. The catalysts were electrochemically characterized by cyclic voltammetry and by oxidation of pre-adsorbed CO. Both electrochemical methods showed characteristics that can be attributed to Pd(100) facets that are predominant on cubic Pd nanoparticles. From cyclic voltammograms the electrochemically active surface area was found, expectedly it increased with increasing Pd content in the catalyst and also with decreasing the particle size. The ORR studies in 0.5 M H2SO4 showed that the half-wave potentials increase with palladium content and with decreasing the particle size, following the changes in the electrochemical surface area. The mass-activity of the catalysts did not depend on the Pd loading, but increased with decreasing the particle size. From the rotating disk electrode studies the number of electrons transferred per O2molecule was found to be near 3.5, showing that some hydrogen peroxide is formed. The Tafel analysis revealed that the ORR mechanism on carbon-supported Pd nanocubes was the same as on bulk Pd. In alkaline media the half-wave potentials were in the same order as in acid solution, but more subtle differences were evident. The Koutecky-Levich analysis of the RDE data showed that the number of electrons transferred per oxygen molecule was 4 in the whole range of potentials studied. The Tafel analysis showed that the rate limiting step is the sluggish transfer of first electron to O2molecule. References 1. E. Antolini, Energy Environ. Sci., 2, 915 (2009). 2. H. Erikson, A. Sarapuu, N. Alexeyeva, K. Tammeveski, J. Solla-Gullon, and J. M. Feliu, Electrochim. Acta, 59, 329 (2012). Figure 1

Irreversible adsorbed bismuth can be used to determine the fraction of (111) domains on a given platinum sample. On Pt(111) electrodes, the surface redox process of adsorbed bismuth takes place at 0.63 V in a well-defined peak. The behavior of this redox process on the Pt(111) vicinal surfaces indicates that the bismuth atoms involved in the redox process are only those deposited on the (111) terrace sites and that the charge under the peak at 0.63 V is directly proportional to the number of sites on (111) ordered domains (terraces). The good linear relationship obtained between the charge for the bismuth redox process and the number of (111) terrace sites on the vicinal surfaces allows construction of a calibration curve. This calibration curve has been used to directly estimate the amount of (111) ordered domain terrace sites on polycrystalline platinum samples with different surface ordered domains. The results agree with what we would expect from our knowledge of these surfaces.

Intensive research has been focused on the study of the production of well-defined structured nanoparticles. This is due to the different properties possessed by these materials according to their size/shape. One of the most studied noble metals is Platinum (Pt) due to its catalytic properties and different methods have been reported to prepared. However, it is of great importance to find easy new ways as well as cost effective and scalable method to synthesize them. In a recent communication [1] we have reported, for the first time, the synthesis of cubic Pt nanoparticles with a very high yield using a water-in-oil (w/o) microemulsion method in which HCl was added in the aqueous phase of the w/o microemulsion. This method, unlike others such as the colloidal method, fulfils these previous requirements. This works pretends to explain the effect on the shape of the nanoparticles of different surface modifiers added in the aqueous phase using also different Pt precursors. In addition, bimetallic nanoparticles have been prepared with similar methodology and the effect of the adsorbates will be evaluated. The nanoparticles have been electrochemically characterised by hydrogen and Ge ads/desorption processes, CO monolayer oxidation and ammonia electro-oxidations have been also studied as test reactions in order to determine the efficiency in the catalytic activity. References [1] R. A. Martínez-Rodríguez, F. J. Vidal-Iglesias, J. Solla-Gullón, C. R. Cabrera, J. M. Feliu, Synthesis of Pt Nanoparticles in Water-in-Oil Microemulsion: Effect of HCl on Their Surface Structure, J. Am. Chem. Soc. 136 (2014) 1280.

Researchers have particular interest in amino-terminated monolayers because they have been used for several applications. Among them, SAMs based on aromatic thiols have been vastly studied. The formation of organic monolayers by self-assembly is directed by a specific interaction between a terminal functional group and the surface, in this case the bond formed between the thiol sulphur and the metal. Aminobenzenethiols (ABTs) are frequently studied as SERS probe molecules and particularly the p-ABT is commonly used as molecular junction and building block in SAMs. Several contributions have been reported about the p-ABT adsorbed on Ag and Au due to the same specific behaviour under certain experimental circumstances. SERS from the self-assembled monolayer of p-ABT on Ag and Au is significantly different from the normal Raman spectrum of the molecule in solid state. In a normal Raman spectrum only bands that correspond to completely symmetric a1 vibrations are observed, but in its SERS spectrum, non-a1-type bands are also present (1143, 1390 and 1432 cm-1). However, the SERS from benzenethiol on these metals are substantially the same as the normal Raman spectrum. It was first speculated [1, 2] that the alteration of the spectrum of p-ABT could be due to the CT mechanism contribution, as a consequence of the alteration of the electronic states of benzenethiol by the introduction of an -NH2 group on the benzene ring. Alternatively, it was shown, based on the spectral similarity of p-ABT and 4,4’-DMAB, that the non-a1-type bands correspond to N=N stretching vibrations of 4,4’-DMAB produced from p-ABT via a catalytic coupling reaction [3]. Recently, the formation of the azo-derivative, observed in the cases of gold and silver surfaces, was not detected on copper surfaces [4] pointing out that the metal could play an important role in the azobenzene derivative formation. In our knowledge no studies have been done with Pt-group metals, which are generally accepted to be weak electromagnetic enhancing metals under conditions of visible wavelength excitation. Consequently, the CT mechanism could play an important role. We report in this work a spectroelectrochemical study with different Pt-group metals, for which a correlation between their voltammetric behaviour and the SERS spectra is established. Figure. (A) SERS spectra and (B) Cyclic voltammetry of p-ABT on Pt nanoparticles depostited on glassy carbon. Test solution: 0.1 M NaClO4 + 0.001 M p-ABT. Sweep rate: 50 mVs-1 [1] Osawa, M., Matsuda, N., Yoshii, K., Uchida, I., J. Phys. Chem. 98 (1994) 12702 [2] Kim, K., Kim, K.L., Shin, K.S., J. Phys. Chem. C 117 (2013) 5975 [3]Huang, Y.F. Zhu, H.P., Liu, G.K., Wu, D.Y., Ren, B. Tian, Z.Q. J. Am. Chem. Soc. 132 (2010) 9244 [4] Dendisova, M., Havranek, L., Oncak, M. Matejka, P. J. Phys. Chem. C 117 (2013) 21245

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The objective of this study is to investigate the catalytic activity of Pt/C, PtSn/C and PtSnNi/C towards ethanol electrooxidation. Water-in-oil microemulsion method has been used since it has been identified as one of the most powerful technique of catalyst preparation; it allows easily varying and controlling the atomic composition of the catalyst. The nanoparticles obtained were characterized by TEM and EDX techniques, showing a well dispersed material on the carbon support with a narrow distribution of sizes. Cyclic voltammetry and chronoamperometry measurements were carried out in acidic medium in the absence and in the presence of ethanol. The water-in-oil microemulsion method was found to be suitable for making active PtSn/C and PtSnNi/C electrocatalysts for ethanol oxidation. The addition of nickel enhances the catalytic activity of PtSn/C electrocatalysts by decreasing onset potential and increasing current density, therefore PtSnNi electrocatalysts represent a promising alternative towards improving ethanol oxidation process.

In this paper we will review the state-of-the-art in the application of shape-controlled metal nanoparticles in Electrocatalysis, especially in reactions of interest in PEMFCs such as O2reduction and CO, methanol, ethanol and formic acid electrooxidations. In particular, we will focus our attention on shape-controlled platinum (Pt), gold (Au) and palladium (Pd) nanoparticles. In addition, electrocatalytic applications of shape-controlled Pt-based alloy nanoparticles will be also reviewed. The results reported will highlight how important can be controlling the shape of the nanocatalyst and how effective this parameter may be to improve the activity and thus, develop highly active electrocatalysts.

The electrosynthesis of L-cysteine (RSH) in aqueous medium has been investigated using Pb particles dispersed on carbon as a cathode for L-cystine electroreduction. Pb particles were synthesized in a water-in-oil microemulsion and later dispersed on carbon Vulcan XC-72. The electrochemical characterization of the Pb/C catalyst was carried out by cyclic voltammetry and scanning electrochemical microscopy (SECM). In particular, an approach of the substrate generation/tip collection mode of the SECM has been used for imaging the RSH generation. Different 20 wt % Pb/C-supported cathodes have been fabricated and morphologically characterized. These cathodes were tested for RSH electrosynthesis and compared with a conventional bulk Pb cathode. After a 100% theoretical charge, our three-dimensional 20 wt % Pb/C cathode exhibits a 30% higher RSH yield and current efficiency than the other cathodes. This performance improvement is related to the increase in the available geometric area of this electrode. We demonstrate the feasibility of using Pb/C particles as a catalyst in a type of cathode for RSH electrosynthesis. Moreover, our Pb/C electrodes show a broad scope because they can be applied to other electrosyntheses of valuable organic compounds where bulk Pb is the conventional cathode at present.

Reactivity towards methanol and formic acid electrooxidation on Pt nanoparticles with well characterised surfaces were studied and compared with the behaviour of single crystal electrodes with basal orientations. Polyoriented and preferential (100), (111) and (100)-(111) Pt nanoparticles were synthesised, cleaned preserving its surface structure, characterised and employed to evaluate the influence of the surface structure/shape of the Pt nanoparticles on these two relevant electrochemical reactions. The results pointed out that, in agreement with fundamental studies with Pt single crystal electrodes, the surface structure of the electrodes plays an important role on the reactivity of both oxidation processes, and thus the electrocatalytic properties strongly depend on the surface structure/shape of the nanoparticles, in particular on the presence of sites with (111) symmetry. These findings open the possibility of designing new and better electrocatalytic materials using decorated shape-controlled Pt nanoparticles as previously described with Pt single crystal electrodes.

The synthesis and electrochemical decontamination of platinum-palladium nanoparticles prepared by reduction with hydrazine of H 2 PtCl 6 and K 2 PdCl 4 in a water-in-oil microemulsion of water/poly(ethylene glycol)-dodecyl ether (BRIJ 30)/n-heptane is reported. X-ray photoelectron spectroscopy experiments were carried out to determine the composition of the nanoparticles obtained. Due to the presence of surfactant molecules coating on the nanoparticles, a decontamination procedure was developed. The decontamination procedure applied allows a cleaning of the surface of the nanoparticles without modification or damage for the crystalline surface structure as a result of synthesis conditions. The influence of the classical electrochemical activation or cleaning of the surface on the electrochemical behavior of the nanoparticles is also compared. The results obtained show a deep modification of the electrocatalytic behavior of the nanoparticles after the electrochemical activation treatment. They demonstrate that this activation process should not he applied in studies where the influence of the size, surface structure, and surface composition of the nanoparticles on their electrocatalytic and catalytic properties are studied.

Electrochemical engineering, a relatively young discipline, has important interrelationships with chemical engineering and electrochemistry. The main objectives of electrochemical engineering are the characterization and optimization, both in design and operation mode, of the mechanisms and the processes related to the conversion of chemical and electrical energies. Among the examples of electrochemical synthesis implemented at an industry scale are the synthesis of chlor–alkali, aluminium, adiponitrile (an intermediate compound in the manufacture of Nylon). It is feasible to review the systems of electric energy generation (batteries and fuel cells) and sewage treatment. The definition of figures of merit is focused on the electrochemical process and is related to its yield. This concept constitutes a very useful tool to optimize the cost and the economic balance of this process. In this paper, the most characteristic figures of merit in an electrochemical process are defined. They are applied using experimental data obtained in an organic electrosynthesis process: the reduction of L-cystine to L-cysteine in acid media.