An XPS study on oxidation states of Pt and its alloys with Co and Cr and its relevance to electroreduction of oxygen

Aricò, A.S.; Shukla, Ashok; Kim, H.; Park, S.; Min, Myoungki; Antonucci, V.

doi:10.1016/s0169-4332(00)00831-x

Cited by 355 publications

(245 citation statements)

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“…The three doublets are identified by the position of the Pt 4f 7/2 peak at binding energies of 71.1 eV, 72.4 eV and 74.0 eV, attributed to the elemental state Pt 0 , oxidized states Pt 2+ and Pt 4+ , respectively. 22 The binding energies are referenced to . The surface oxidation of Pt upon exposure to the air is expectable, as oxygen is readily chemisorbed onto the surface of Pt nanoparticles, especially at the kink and step sites of the nanocrystals.…”

Section: Resultsmentioning

confidence: 99%

Graphene-Carbon Nanotube Hybrids as Robust Catalyst Supports in Proton Exchange Membrane Fuel Cells

Pham

McPhail

Mattevi

et al. 2016

J. Electrochem. Soc.

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Catalyst degradation is one major challenge preventing the worldwide commercialization of the Proton Exchange Membrane Fuel Cells. In this study, we investigate the development of a novel hierarchical carbonaceous support for the platinum catalysts, called graphene-carbon nanotube hybrids (GCNT), and its degradation behavior during an accelerated degradation test. The carbon support is fabricated by growing graphene directly onto carbon nanotubes to form a unique all-carbon nanostructure possessing both an ultra-high density of exposed graphitic edges of graphene and a porous structure of carbon nanotubes. The GCNT-supported platinum catalyst exhibits a higher intrinsic catalytic activity than a carbon black-supported platinum catalyst, and much higher than a CNT-supported platinum catalyst. The enhanced catalytic activity of the GCNT-supported platinum catalyst is explained by the high graphitic edge density which promotes the catalytic reactions on platinum catalyst. The GCNT-supported platinum catalyst also exhibits a superior electrochemical stability over that of the carbon black-supported platinum catalyst, explained by the high crystallinity of the GCNT support. The superior stability is expressed by a lower loss in polarization performance, a smaller increase in charge transfer resistance, a lower loss in the platinum electrochemical surface area, a lower rate of carbon corrosion, and a more stable catalyst microstructure. Energy security and climate change have become major global concerns, and viable candidates for renewable energy technologies are actively being sought. With high energy conversion efficiencies and low emissions, fuel cell technologies have received much research attention recently.

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Section: Resultsmentioning

confidence: 99%

Graphene-Carbon Nanotube Hybrids as Robust Catalyst Supports in Proton Exchange Membrane Fuel Cells

Pham

McPhail

Mattevi

et al. 2016

J. Electrochem. Soc.

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“…Even though the effect for ORR is almost the same using Pt 3 Sn/C and Pt/C ETEK, further studies described in this paper have shown that Pt 3 Sn/C presents a higher electrocatalytic activity than Pt/C ETEK for ORR, using ethanol in the electrolyte. The effect observed for the material here highlights the value of Pt 3 Sn/C PPM, which is derived from the electronic effects caused by changes in the platinum "d" band levels (Min, Cho et al, 2000;Aricò, Shukla et al, 2001;Shukla, Neergat et al, 2001;Lima, Lizcano-Valbuena et al, 2006). The onset potentials for the ORR were similar for the two electrocatalysts (see Table I).…”

Section: Electrochemical Experimentsmentioning

confidence: 55%

“…Using Pt/C ETEK, the diffusion limit mass current density for the ORR was 20 % smaller than that using the same electrocatalyst without ethanol. These results can be explained because the strength of adsorption of both CO (Tong, Kim et al, 2002;Alayoglu, Nilekar et al, 2008;Park, Lee et al, 2008) and O 2 (Min, Cho et al, 2000;Aricò, Shukla et al, 2001;Shukla, Neergat et al, 2001;Lima, Lizcano-Valbuena et al, 2006) is reduced in Pt 3 Sn alloy materials, thereby facilitating a release of the catalytic sites and increase of the kinetic reaction.…”

Section: Electrochemical Experimentsmentioning

confidence: 99%

“…This fact has been attributed to changes in the Pt-Pt bond distance, the number of Pt nearest neighbors, the electron density of states in the Pt 5d band and the nature and coverage of surface oxide layers (Min, Cho et al, 2000;Aricò, Shukla et al, 2001;Shukla, Neergat et al, 2001;Lima, Lizcano-Valbuena et al, 2006). This increase in kinetics occurs because the oxygen reduction activity increases with a decrease in the adsorption strength of the oxygenated species.…”

Section: Introductionmentioning

confidence: 99%

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A Pt3Sn/C Electrocatalyst Used as the Cathode and Anode in a Single Direct Ethanol Fuel Cell

Parreira¹,

Rascio²,

Silva³

et al. 2012

IJC

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This paper presents a study involving the use of Pt 3 Sn/C electrocatalysts as cathodes and anodes in a single direct ethanol fuel cell. First, we studied the oxygen reduction reaction (ORR) using commercial Pt/C from ETEK and Pt 3 Sn/C as electrocatalysts with an alloy degree of 92 %. The electrocatalytic activity of the material for oxygen reduction was assessed using the rotating disk electrode technique (RDE). When Pt 3 Sn was tested for ORR in the presence of ethanol, the results showed greater tolerance to the cross-over effect than Pt/C in the electrochemical cell. The experiments in a single direct ethanol fuel cell showed that without oxygen pressurization of the cell, the maximum power density is higher using Pt 3 Sn/C as both cathode and anode than using Pt 3 Sn as an anode and Pt/C as a cathode. When using Pt 3 Sn/C as both the cathode and anode in a direct ethanol fuel cell, cell performance enhances.

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“…A mobilidade dos átomos de platina sobre substrato de carbono é dificultada quando o ferro está presente. Aricò e colaboradores 33 realizaram estudos de difração de raios X para Pt, Pt-Co e Pt-CoCr e os resultados mostraram que a Pt suportada em carbono tem estrutura cúbica de face centrada, porém, Pt-Co e Pt-Co-Cr suportadas em carbono têm estrutura de face centrada tetragonal, o que está de acordo com a proposta de Glass 29 . Outros estudos em ligas de Pt-Co suportadas em carbono mostraram que uma estrutura cristalina desordenada é mais resistente à corrosão que uma ordenada e mantém alta a atividade catalítica deste material por um longo tempo 17 .…”

Section: Eletrocatálise Da Reação De Redução De Oxigêniounclassified

Eletrocatálise das reações de oxidação de hidrogênio e de redução de oxigênio

Ticianelli¹,

Câmara²,

Santos³

2005

Quím. Nova

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Recebido em 6/7/04; aceito em 3/11/04; publicado na web em 28/2/05 ELECTROCATALYSIS OF THE HYDROGEN OXIDATION AND OXYGEN REDUCTION REACTIONS. This work discusses the electrocatalytic processes taking place in the polymer electrolyte fuel cell electrodes, specifically the hydrogen oxidation reaction (HOR) and the oxygen reduction reaction (ORR), because these are clear examples of electrochemical reactions favored by the use of electrocatalysts. Since the gaseous reactants are very little soluble in the electrolyte, the use of special electrodes, named gas diffusion electrodes, is required to promote easy and continuous access of reactant gases to the electrocatalytic sites. Besides this, other important aspects such as the use of spectroscopic techniques and of theoretical models to improve the knowledge of the electrocatalytic systems are shortly discussed.Keywords: electrocatalysis; hydrogen oxidation reaction; oxygen reduction reaction. INTRODUÇÃOO termo Eletrocatálise começou a ser difundido a partir da dé-cada de 60, na discussão da influência do material do eletrodo sobre a cinética da reação eletroquímica de desprendimento de hidrogênio. Nos dias de hoje, o uso do termo tornou-se muito mais abrangente, referindo-se genericamente ao efeito da natureza do material do eletrodo sobre a cinética de qualquer reação eletroquímica. Na maioria dos casos, o eletrodo não é transformado durante a ocorrência da reação, servindo apenas como um aceitador ou doador de elétrons e participando do processo através de etapas de adsorção de reagentes e/ou intermediários.Neste contexto, verifica-se que os fundamentos que governam as propriedades eletrocatalíticas têm muito em comum com aqueles da catálise heterogênea. Assim, diversos aspectos, muitos deles comuns à catálise heterogênea, governam os processos eletrocatalíticos: (1) a atividade eletrocatalítica é função da estrutura eletrônica dos átomos da superfície do material que compõe o eletrodo e (2) as propriedades superficiais, químicas e estruturais são fundamentais na definição da velocidade e do caminho da reação. Específico da eletrocatálise é o fato de que nos processos eletroquímicos estão sempre envolvidas reações de transferência de carga, sendo possível modificar a energia de ativação e/ou as propriedades da superfície ativa através do controle do potencial do eletrodo.Inúmeras reações eletroquímicas com potencial tecnológico somente são viabilizadas quando realizadas sob condições que garantam uma velocidade (ou corrente elétrica) adequada, ou seja, com uso de materiais eletródicos que apresentem elevada eficiên-cia eletrocatalítica. Em sistemas operacionais, fatores associados ao transporte de massa podem também se tornar etapas importantes no processo global de transferência de carga e, assim, a extensão da área superficial desempenha um papel crucial sobre sua velocidade. Neste trabalho são discutidos os processos eletrocatalíticos que ocorrem nas células a combustível com eletrólito polimérico (PEMFC), ou seja, as reações de oxidação de hidrogênio (ROH) e ...

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An XPS study on oxidation states of Pt and its alloys with Co and Cr and its relevance to electroreduction of oxygen

Cited by 355 publications

References 28 publications

Graphene-Carbon Nanotube Hybrids as Robust Catalyst Supports in Proton Exchange Membrane Fuel Cells

Graphene-Carbon Nanotube Hybrids as Robust Catalyst Supports in Proton Exchange Membrane Fuel Cells

A Pt3Sn/C Electrocatalyst Used as the Cathode and Anode in a Single Direct Ethanol Fuel Cell

Eletrocatálise das reações de oxidação de hidrogênio e de redução de oxigênio

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