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Bimetallic oxides and MOFs have been used as catalysts for the ORR

Co–Mo materials have been reported as electrocatalysts that present good performance in alkaline electrolytes. In this paper, the addition of copper into Co–Mo catalysts was evaluated for the hydrogen evolution reaction (HER). It was observed that the electrochemical activity of the Co–Mo for the HER benefited from the addition of copper. The overpotentials required to reach a current density of −10 mA cm−2 were of −156 mV and −119 mV for Co67Mo33 and Co56Mo21Cu23, respectively. Besides the increased surface area resulting from the addition of copper, it was observed that the improved intrinsic activity for Co61Mo32Cu7, compared to Co67Mo33, is related to a thermodynamic favoring of the hydrogen adsorption and desorption stages. Large quantities of copper do not favor the HER; therefore, the increased catalytic activity depends on a balance between the intrinsic catalytic activity and the increase of the electroactive area.

Made available in DSpace on 2020-12-12T02:30:34Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-02-01 The high levels of atmospheric CO2 transformed this compound in a preoccupant pollutant. However, a wide range of semiconductors, including bismuth vanadate (BiVO4), can be applied for CO2 reduction aiming generation of fuels. This work reports the optimization of the BiVO4 layer synthesis by microwave system using factorial experimental design, where the variables time (5 to 15»min) and temperature (120 to 160»°C) were studied. For evaluation purposes, the materials synthetized were applied in photocatalytic reduction of CO2. All the BiVO4 materials analyzed promoted the formation of methanol. The best condition was obtained under the material synthesized at 160»°C with 15»min of reaction, where 1.5»mmol L-1 gcat-1 of methanol was produced after 120»min of photocatalysis. For the first time, acetone formation was observed in this kind of material. The best condition for acetone production was acquire with the material prepared at 140»°C with 10»min of synthesis, where 0.030»mmol L-1 gcat-1 was generated after 240»min of CO2 reduction. Differences in methanol concentration obtained among the samples were probably related to crystallographic patterns of the material, once the presence of Bi2O3 or other BiVO4 crystallographic species may affect the efficiency of the material. The results obtained in this work show that the use of BiVO4 layer semiconductor prepared by microwave system for CO2 reduction leads to the generation of high amounts of methanol under just UV-vis light incidence, aside from promoting the production of acetone. Department of Chemistry Federal University of São Carlos, Rod. Washington Luiz, Km 235 Institute of Chemistry - Araraquara UNESP Bairro Quitandinha, Rua Francisco Degni, 55 Institute of Chemistry - Araraquara UNESP Bairro Quitandinha, Rua Francisco Degni, 55

Glycerol is an important biomass-derived product with potential to be applied on energy converting systems or as platform molecule in electrosynthesis. In this work we studied the glycerol oxidation reaction (GOR) in alkaline media containing distinct alkaline cations and controlling the mass transport. The cyclic voltammograms were deconvoluted into three processes and the changes in the charge of each process revealed that mass transport affects the GOR in a complex matter, depending on both applied potential and electrolyte cation. Regardless of the cation on supporting electrolyte, high-performance liquid chromatography (HPLC) analysis revealed the production of glycerate and lactate during GOR. Finally, potential oscillations under current control were mapped, highlighting the influence of both cations and mass transport, even in the systems with very similar behavior under potential control. The authors thank to the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001 and the Conselho Nacional de Pesquisa e Desenvolvimento (CNPq), for fellowships and grants (#430426/2018-6). The authors also thank the São Paulo Research Foundation (FAPESP) (Grants #2013/07296-2, #2014/50249-8, #2017/11986-5, #2018/20952-0 and #2019/00305-2), Shell, and the strategic importance of the support given by ANP (Brazil's National Oil, Natural Gas and Biofuels Agency) through the R&D levy regulation.

To prevent sintering of carbon supported metal nanoparticles during high temperature annealing in reductive conditions, Pt-Sn nanoparticles were coated with MgO. The agglomeration of Pt-Sn particles upon thermal annealing was significantly inhibited with a MgO shell. The presence of the oxide shell gave rise to a more homogeneous microstructure and a better electrochemical stability.

Made available in DSpace on 2021-06-25T10:11:01Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-15 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) BiVO4 is a non-titania inorganic photocatalyst recognized as an effective visible-light-driven semiconductor that has been shown to be effective for CO2 reduction. However, some characteristics, such as a low separation rate of photogenerated electron-hole pairs and low mobility of electron-hole carriers, are still challenges to the widespread use of this semiconductor. In this paper, the influence of metallic Bi on the CO2 photoreduction activity was evaluated for the BiVO4 semiconductor. Bi–BiVO4 catalysts were prepared by microwave heating at 240 °C, employing different reaction times and magnetic stirring regimes. Metallic Bi improved the catalytic activity of BiVO4 for CO2 reduction, enhancing the absorption of visible light and promoting internal photoemission of electrons in the metal-semiconductor interface, which improves the electron density in the surface of the catalyst. This resulted in an astonishing concentration of methanol; Bi–BiVO4 prepared at 240 °C, for 5 min, and without magnetic stirring, produces around 5.0 mmol L−1 g−1catalyst of methanol and 40 μmol L−1 g−1catalyst of acetone after 240 min of reaction. The mechanism of charge transfer between the BiVO4 and the metallic Bi is influenced by the size of the microsphere crystallites, moreover, the production of methanol increased as the Bi grain size decreased. Department of Chemistry Federal University of São Carlos, Rod. Washington Luiz, Km 235, São Carlos-SP Institute of Chemistry - Araraquara UNESP, Rua Francisco Degni, 55, Bairro Quitandinha, SP Department of Chemistry University of Bath, Claverton Down Institute of Chemistry - Araraquara UNESP, Rua Francisco Degni, 55, Bairro Quitandinha, SP FAPESP: #2017/1198-5 CAPES: 001 FAPESP: 2013/07296-2 FAPESP: 2014/50249-8 FAPESP: 2018/02950-0 FAPESP: 2018/16401-8

Rare earths (RE) have been studied in the literature as additives in Pt and PtSn catalysts for the ethanol oxidation reaction (EOR), but their stability and influence on the mechanism of the EOR have not been reported. In this work, PtSnRE/C (RE: La, Ce, and Pr) catalysts were obtained by the polyol method, characterized, and their stability toward the EOR evaluated by cycling at two different potential ranges. The accelerated aging tests indicated that despite the changes in the CO stripping profiles, the ternary catalysts exhibit higher current densities after aging than Pt/C and PtSn/C catalysts. Even after dissolution of the rare-earth metals, as observed by energy-dispersive X-ray spectroscopy (EDS) before and after aging, the EOR activity after short-term stability tests was found to be higher than the initial one. The addition of these metals facilitates the retention of tin in the material, contributing to the overall stability of the bimetallic catalyst. The oxidation products of the ternary catalysts were evaluated by in situ Fourier transform infrared spectroscopy (FTIR) spectroscopy and high-performance liquid chromatography (HPLC), where the major products were found to be acetaldehyde and acetic acid, with only small concentrations of CO2. The improvement in the ethanol oxidation efficiency by PtSnRE/C catalysts can be explained by a bifunctional mechanism in which the rare-earth oxides are able to provide oxygenated species at low potentials.

Sugarcane bagasse ash sand (SBAS) can be used as a bioadditive in concrete. However, little is known about its effects on the steel corrosion process. This paper reports the evaluation of the corrosion susceptibilities of steel immersed in simulate concrete pore solutions, with addition of SBAS, to understand the corrosion process in reinforced structure. The open-circuit potential profiles and polarisation curves suggested the favourable formation of a passive film on the steel immersed in the SBAS-containing medium. Electrochemical impedance spectroscopy confirmed that the SBAS-containing medium presents better passivating properties, showing that this recycled material can be used as corrosion inhibitor for reinforced concrete, encouraging its use in the civil industry.

The study of metallic multilayers (MM) has presented interesting highlights to understand electrocatalytic properties for organic molecules oxidation. This work reports the preparation and characterization of MM using rhodium or ruthenium as an intermediate layer, Ptpc/Rh/Pt and Ptpc/Ru/Pt, aiming to evaluate the electrocatalytic activity toward methanol and ethanol oxidation in acid medium. For methanol electro-oxidation, the evaluated MM presented higher current density than Ptpc, especially Ptpc/Rh2/Pt1 and Ptpc/Ru5/Pt2, where the increase in peak current density was 283% and 422% compared to Ptpc. By in situ infrared spectroscopy (FTIR in situ), it was observed that in MM the CO2 formation from methanol oxidation occurred in lower potentials compared to Ptpc. In the ethanol oxidation, Ptpc/Rh2/Pt1 and Ptpc/Ru5/Pt2 increase in peak current density 32% and 67% compared to Ptpc, respectively. The bands referring to the acetaldehyde, acetic acid and CO2 were observed first to MM than for Ptpc. The better electroactivity of the metallic multilayers in the electro-oxidation of alcohols could be explained by the changes in the electronic interaction between the exposed platinum surface and the rhodium or ruthenium intermediate layer, which facilitated the oxidation of intermediates at lower potentials, and thus, increasing of the electrocatalytic activity of these materials.

Ternary Pt–Sn–Ce/C catalysts were prepared by a modified formic acid method, and their activity for the ethanol oxidation reaction (EOR) was compared to that of Pt–Sn/C, Pt–Ce/C and Pt/C catalysts. No bulk alloy formation was detected by XRD analysis. XPS measurements indicated no segregation on the catalyst surface and the presence of Sn(0) and SnO x , Ce 2 O 3 and CeO 2 oxides. The onset potential for CH 3 CH 2 OH oxidation on Pt–Sn/C and Pt–Sn–Ce/C (60:20:20) catalysts, which have the highest Sn content on the surface, was lower than that of Pt–Sn–Ce/C (70:20:10) and (50:20:30), Pt–Ce/C and Pt/C catalysts. This work highlights the dependence on the potential of the effect of cerium in Pt–Sn–Ce/C catalysts on the EOR activity and on the reaction mechanism. By derivative voltammograms, different reaction pathways at different potentials, involving Sn (at ca. 0.44 V vs. RHE), Sn + Ce (at ca. 0.55 V vs. RHE) and Ce (at ca. 0.67 V vs. RHE) were inferred. The Pt–Sn–Ce/C catalysts were less tolerant to poisoning by ethanol oxidation intermediate species than Pt/C and Pt–Sn/C, but more stable than Pt–Ce/C catalysts. DEFC tests at 90 °C indicated that a higher Sn surface content is more effective for ethanol oxidation than the addition of Ce to Pt–Sn/C.

Ternary Pt–Sn–Pr/C (70:10:20), (70:15:15) and (45:45:10) electro-catalysts were prepared by a modified formic acid method, and their activity for the ethanol oxidation reaction (EOR) was compared with that of Pt–Pr/C catalysts prepared by the same methods and that of commercial Pt–Sn/C (75:25) and Pt/C catalysts. Among all the catalysts, the Pt–Sn–Pr/C (45:45:10) catalyst presented both the highest mass activity and the highest specific activity. The steady state electrochemical stability of ternary Pt–Sn–Pr catalysts increased with the surface Sn/Pt atomic ratio. Following repetitive potential cycling (RPC), the activity for ethanol oxidation of Pt–Sn–Pr/C catalysts with high surface Sn/Pt atomic ratio was considerably higher than that of the corresponding as-prepared catalysts, and increased with increasing the Sn/Pt ratio. The increase of the EOR mass activity following RPC was ascribed to the increase of either the specific activity (for the Pt–Sn–Pr/C (70:15:15) catalyst) or the electrochemically active surface area (for the Pt–Sn–Pr/C (45:45:10) catalyst). Dissolution of Sn and Pr oxides from Pt–Sn–Pr/C catalyst surface was observed following RPC.

Sistemas de células a combustível alimentadas por etanol (DEFC - Direct Ethanol Fuel Cell) são vistos como candidatos para ajudar preencher a lacuna entre a demanda e oferta de energia elétrica. Entretanto, as DEFC ainda não apresentam desempenho tão elevado, que incentivem a comercialização. Um dos principais esforços para elevar o desempenho é obter catalisadores anódicos mais eletroativos e estáveis para reação de oxidação de etanol (ROE). Neste trabalho, visou-se obter e avaliar catalisadores Pt-Sn-Terras raras (La, Ce, Pr e Eu) para ROE. Os catalisadores foram sintetizados a partir de algumas modificações do método do poliol; caracterizados fisicamente, por técnicas de EDX, ICP, ATG, DRX, TEM, XPS e XAS; e caracterizados eletroquimicamente em células de três eletrodos e em células unitárias. O método de síntese promoveu tamanhos médios de partícula entre 3,0 a 4,5 nm para catalisadores PtSnTR/C (TR: La, Ce, Pr e Eu), um dos menores valores reportados para esse tipo de material. Por DRX, foi possível verificar que a síntese promoveu um certo grau de liga Pt-Sn. Por XPS, confirmou-se a presença de Pt e Sn metálicos, óxidos de estanho e de platina, e terras raras em forma de óxidos mistos. Por XAS, observou-se que os metais adicionados promoveram um preenchimento da banda 5d da Pt. As caracterizações eletroquímicas indicaram maior densidade de corrente na ROE para os materiais ternários PtSnTR/C 75:20:05 do que os catalisadores Pt/C, e que PtSn/C 60:40, na maioria dos casos. Os testes de envelhecimento acelerado indicaram que, mesmo com a alteração dos perfis voltamétricos, os catalisadores ternários apresentaram menores perdas na atividade que os catalisadores Pt/C e PtSn/C. Ao caracterizar os produtos da oxidação dos catalisadores por FTIR e HPLC, observou-se que os produtos majoritários foram acetaldeído e ácido acético; e apenas uma pequena formação de CO2 foi detectada . A adição de terras raras, em baixas concentrações, aumentou a atividade eletrocatalítica dos catalisadores Pt/C e PtSn/C provavelmente por disponibilizar espécies oxidadas a baixos potenciais, favorecendo a oxidação de intermediários da ROE, e contribuiu para a estabilidade dos catalisadores PtSn/C. Direct ethanol fuel cell (DEFC) systems are seen as candidates to fill the gap between demand and supply of electric electricity. However, the DEFC\'s performance does not encourage its large commercialization yet. One of the main efforts to increase the performance is obtaining more electroactive and stable anodic catalysts for the ethanol oxidation reaction (EOR). In this work, Pt-Sn-Rare Earth catalysts (La, Ce, Pr and Eu) were obtained and evaluated for EOR. The catalysts were synthesized using polyol method with some modifications; physically characterized by XDS, ICP, TGA, XRD, TEM, XPS and XAS techniques; the electrochemical characterization involved tests on three electrodes cell and on unit cell systems. The synthesis method promoted mean particle sizes between 3.0 and 4.5 nm for PtSnRE/C catalysts (RE: La, Ce, Pr and Eu), one of the smallest values reported for this type of material. By XRD, it was observed some degree of Pt-Sn alloy. The presence of Pt and Sn metallic, tin and platinum oxides, and rare earths in the form of mixed oxides were confirmed by XPS. The added metals promoted a fill of the Pt 5d band, as observed by XAS. Electrochemical characterizations indicated higher current density in the EOR for the ternary materials than Pt/C catalysts and PtSn/C 60:40, in most of cases. The accelerated aging tests indicated that, even with voltammetric profiles changes, the ternary catalysts had lower losses in the activity than the Pt/C and PtSn/C catalysts. By FTIR and HPLC, it was observed that the main products were acetaldehyde and acetic acid; and small concentration of CO2 was detected. The low addition of rare earths increased the electrocatalytic activity of Pt/C and PtSn/C catalysts probably because they promoted more oxidized species at low potentials, favoring the intermediates oxidation of the EOR, and contributed to PtSn/C catalysts stability.

Pt–Pr/C electrocatalysts were prepared by a modified formic acid method, and their activity for carbon monoxide and ethanol oxidation, their short term stability and durability were compared to that of commercial Pt/C and Pt–Sn/C (3:1) catalysts. By derivative voltammetry (DV) it was found that ethanol electro-oxidation takes place by two main pathways at different potentials. It was observed that, in the presence of Pr, ethanol electro-oxidation takes place mostly through the pathway at lower potential, which is the most interesting for fuel cell application. The Pt–Pr/C catalysts were less tolerant to poisoning by ethanol oxidation intermediate species than Pt/C. Durability test by a repetitive potential cycling under Ar atmosphere revealed a good structural stability of Pt–Pr/C catalysts. A repetitive potential cycling under CO atmosphere carried out on the Pt–Pr/C (1:1) catalyst, instead, indicated a structural change, likely by formation of a core–shell structure.

In the present work, an innovative methodology is used to contribute in the elucidation of methanol electro-oxidation reaction on polycrystalline Pt surface. We coupled infrared spectroscopy to linear voltammetry and evaluate the data using parallel factor analysis (PARAFAC) to extract hidden information concerning the oxidation reaction. Five adsorbed species were simultaneously extracted and quantified at different applied potentials corresponding to: formate, sulfate, water, total CO and COL shift. It was observed that the CO adsorbed content starts at maximum on low potentials and gradually decreases up to 1.0 V. Meanwhile, the interfacial water content on the surface of the CO-free Pt increases, which causes the shift on the COL band, resulting in a further decrease of the interfacial water content. The water content increases again until up to 0.8 V, which it reaches a constant value, due to formate production and subsequent adsorption of sulfate. Using this technique, it was possible to determine the potential window where each chemical species is adsorbed on the surface, as well as the effect of methanol concentration and scan rate on the mechanism.

The mechanism of AISI 1005 corrosion in sulfide ion solutions has been investigated using cyclic voltammetry, electrochemical impedance spectroscopy, X-ray diffraction (XRD) and Mossbauer spectroscopy (MS). The proposed mechanism occurs with the initial formation of oxygenated ferrous species followed by adsorption of HS − species, precipitation of iron monosulfides and their partial conversion to bisulfide iron. This mechanism was demonstrated by XRD results that revealed Fe-O and Fe-S phases and by MS results that detected pyrite as the major proportion (94%) of the iron species in the corrosion product.

Pt–Ln/C (Ln = La, Ce, Pr, and Eu) catalysts were obtained by using a modification of the polyol method and tested for ethanol oxidation. Transmission electron microscopy (TEM) results showed that the Pt–Ln/C catalysts had particles with average size of 3 nm, which is the smallest particle size reported for Pt–rare earth catalysts; and the particles are homogeneously distributed on the carbon support. X-ray diffraction analysis showed no alloy formation between Pt and rare earth elements, and X-ray photoelectron spectroscopy (XPS) confirmed that Ln is present in its oxide form. X-ray absorption spectroscopy (XAS) results confirmed that the presence of the second metal affects the Pt electronic structure. CO oxidation in the presence of rare earths takes place mostly through the lower-potential pathway, and these catalysts showed better activity toward ethanol oxidation than Pt/C with the same particle size. Durability tests performed by repetitive potential cycling under an Ar atmosphere revealed good structural stability of the Pt–Ln/C catalysts.

The effect of alloying degree on the ethanol oxidation activity of a PtRu/C catalyst with a Pt/Ru atomic ratio of 1:1 was investigated by measurements in a half-cell and in a single direct ethanol fuel cell. The increase of the amount of Ru alloyed from one third to two thirds of the total Ru content in the catalyst clearly resulted in a decrease of the ethanol oxidation activity. As the amount of the highly active hydrous ruthenium oxide was near the same, the lower activity of the PtRu/C catalyst with higher alloying degree was mainly ascribed to the presence of an excessive number of Ru atoms around Pt active sites, hindering ethanol adsorption on Pt sites. The reduced ethanol adsorption could be also related to the decreased Pt–Pt bond distance and to the electronic effects by alloying.

O efeito da presença do praseodímio em catalisadores de Pt/C e PtSn/C para eletro-oxidação de etanol foi estudado neste trabalho. Os principais objetivos foram estudar alterações na rota sintética da metodologia do ácido fórmico, visando catalisadores com propriedades físico-químicas que aumentem a eficiência frente a reação de oxidação de etanol; entender o motivo das variações na atividade catalítica; e avaliar a estabilidade dos catalisadores nas condições de operação da célula. A atmosfera de síntese dos catalisadores de PtPr/C influencia fortemente as atividades catalíticas destes materiais. Os catalisadores sintetizados em atmosfera de CO apresentaram antecipação do potencial de pico de oxidação de CO e maior área ativa em relação aos materiais sintetizados em atmosfera de hidrogênio. A mudança de atmosfera para gás CO promoveu mudanças físicas como a redução do tamanho médio de cristalito e tamanho médio de partícula. A adição de praseodímio promove a oxidação do etanol em menores potenciais que a platina, por favorecer o mecanismo bifuncional. A adição de estanho ao catalisador PtPr/C teve um efeito benéfico na atividade catalítica. Os dados DRX não indicam alto grau de liga Pt-Sn, mas mesmo em forma de óxido, o estanho apresentou um efeito eletrônico, como informado pelos dados de XAS. A interação de Pt-Sn promove a dissociação da água para formar Sn-OHad próximo a espécies de monóxido de carbono adsorvidas na Pt, facilitando a rápida oxidação de etanol. Os testes de estabilidade indicaram que os catalisadores PtSnPr/C apresentam grande variação da área ativa com sucessivas ciclagens. Apesar da dissolução de espécies de estanho, a adição de praseodímio contribuiu para elevar a estabilidade dos catalisadores sintetizados. The effect of praseodymium presence in Pt/C and PtSn/C catalysts for ethanol electro-oxidation was investigated. The main objectives were the evaluation of a modified formic acid synthesis method for the preparation of PtPr/C and PtSnPr/C catalysts with enhanced activity for the ethanol oxidation reaction and stability at the cell operating conditions. The synthesis atmosphere of PtPr/C catalysts highly influences the catalytic activity of these materials. The catalysts synthesized in CO atmosphere showed a lower onset potential for CO oxidation and a higher active surface area than those synthesized in a hydrogen atmosphere. The CO atmosphere promoted physical changes such as reduction of crystallite size and particle size. Addition of praseodymium to Pt/C catalyst improved the activity for ethanol oxidation by the bifunctional mechanism. Tin addition to the PtPr/C catalyst had a beneficial effect on catalytic activity. XRD data no indicated Pt-Sn alloy, but even in oxide form, tin presented an electronic effect, as reported by XAS data. The interaction of Pt with Sn promotes the dissociation of water to form Sn-OHadsorbed close to carbon monoxide adsorbed on the Pt, and it facilitates a fast ethanol oxidation. Stability tests showed a change in the active area of the PtSnPr/C catalysts after repetitive potential cycling. Although the tin species dissolution, the praseodymium addition increased the catalysts stability.

In the last years, direct ethanol fuel cells (DEFC) have emerged as a promising energy conversion system for portable applications. Efforts for improving the Pt electrode activity have been focused on the addition of co-catalysts able to provide external oxygen-like species at low potentials. Up to now, Pt–Sn materials seem to be the most effective catalysts for ethanol oxidation but improvements are essential for the commercialization of this technology, especially in alkaline medium [1, 2]. The rare earth oxides have a number of features that make them interesting for catalysis and also for ethanol oxidation reaction (EOR) [3-5]. The development of effective and durable electrocatalysts for alcohol electrooxidation becomes one of the goal to achieve the commercialization of DEFC. In this work, PtSn/C and PtSnEu/C were synthesized by two different routes: bromide anion exchange (BAE) method and microwave-assisted heating polyol (MWP). The trimetallic PtSnRE/C (RE: La, Ce and Pr) nanomaterials were obtained by BAE route [6]. The nanomaterials were physically characterized by inductively coupled plasma-optical emission spectrometry (ICP-OES), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results from ICP measurements revealed the presence of platinum, rare earth metal and tin in the materials obtained from both synthesis methods. No-alloy of Pt-Sn or Pt-Rare earth was observed from XRD data of materials obtained by BAE method. Probably the second added metal could be in oxides and amorphous oxy-hydroxides states. The XPS investigations permitted to confirm that tin and the rare earths were mostly in oxide form. The active area of each electrocatalyst was estimated from CO-stripping in a three-electrode cell and the current densities resulted in the EOR are higher for catalysts prepared from BAE. The in situ Fourier Transform Infrared Spectroscopy (FTIRS) technique was helpful to confirm that catalysts obtained by MWP method were less effective towards a complete ethanol oxidation. The addition of tin and rare earth in the material compositions obtained by BAE method did not change the EOR mechanism, but promoted a shift of the onset potential towards lower values. The effects of tin and rare earth were over their ability of providing oxygen species, which leads to a bifunctional mechanism. The difference in activity can probably be explained by electronic and structure changes that enhance the ethanol oxidation reaction. Acknowledgments: São Paulo Research Foundation (FAPESP, grant#2012/12189-8; grant#2015/13218-0) and Brazilian National Nanotechnology Laboratory (LNNano, Project XPS-20257). References: 1) Wang, L. Q., et al. Chemcatchem 7, 2214-2221 (2015). 2) Antolini, E. J Power Sources 170, 1-12 (2007). 3) Antolini, E. and Perez, J. International Journal of Hydrogen Energy 36, 15752-15765 (2011). 4) Corradini, P. G., et al. Phys Chem Chem Phys 15, 11730-11739 (2013). 5) Corradini, P. G., et al. J Power Sources 275, 377-383 (2015). 6) Holade, Y., et al. Catalysts 5, 310-348 (2015).

Pt–Pr/C electrocatalysts were prepared using a modified formic acid method, and their activity for carbon monoxide and ethanol oxidation was compared to Pt/C. No appreciable alloy formation was detected by XRD analysis. By TEM measurements it was found that Pt particle size increases with an increasing Pr content in the catalysts and with decreasing metal precursor addition time. XPS measurements indicated Pt segregation on the catalyst surface and the presence of Pr2O3 and PrO2 oxides. The addition of Pr increased the electro-catalytic activity of Pt for both CO and CH3CH2OH oxidation. The enhanced activity of Pt–Pr/C catalysts was ascribed to both an electronic effect, caused by the presence of Pr2O3, and the bi-functional mechanism, caused by the presence of PrO2.

The effect of the relationship between particle size (d), inter-particle distance (x i ), and metal loading (y) of carbon supported fuel cell Pt or PtRu catalysts on their catalytic activity, based on the optimum d (2.5–3 nm) and x i /d (>5) values, was evaluated. It was found that for y