Determination of the morphology factor of oxide layers

Silva, Leonardo M. Da; Faria, Luiz A. De; Boodts, Julien Françoise Coleta

doi:10.1016/s0013-4686(01)00738-1

Cited by 162 publications

(125 citation statements)

References 21 publications

Supporting

Mentioning

111

Contrasting

Unclassified

Order By: Relevance

Section: Voltammetric Curvessupporting

confidence: 93%

“…q a is seen to increase strongly with the introduction of RuO 2 into the coating, reaching a maximum at 50-70 mol% nominal RuO 2 content. Such behavior is in good agreement with previous work conduced by Da Silva et al 20,21 who reported for sulfuric acid solution a maximum in q a and differential capacity values, for the same interval of nominal composition.Except for the Ti/Co 3 O 4 electrode, all other coatings presented a q a /q c -value close to one (see inset Figure 2). This finding indicates reversibility of the solid state surface redox transitions in slightly acid chloride medium.…”

supporting

confidence: 93%

“…A strategy to compatibilise the lower cost of the spinel oxides with their instability under acid conditions is the formation of mixed rutile + spinel oxides. [17][18][19] Recent studies of the OER on Ti/[RuO 2 +Co 3 O 4 ] coatings by Da Silva et al 17,20,21 showed these mixed oxides present interesting fundamental properties; stabilise the spinel under acid conditions and show an increase of the true electrocatalytic activity. Now we report the results of a detailed investigation of the kinetics and electrocatalytic properties of the Ti/[RuO 2 +Co 3 O 4 ] system for the ClER.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Chlorine evolution reaction at Ti/(RuO2+Co3O4) electrodes

Silva¹,

Boodts²,

Faria³

2003

J. Braz. Chem. Soc.

View full text Add to dashboard Cite

A investigação do mecanismo eletródico e das propriedades eletrocatalíticas da reação de desprendimento de cloro, RDCl, foi executada em eletrodos mistos de óxido do tipo rutila e espinélio de composição nominal Ti/[RuO 2 (x)+Co 3 O 4 (1-x)]. Os eletrodos foram preparados por decomposição térmica (T calc. = 470 o C; t calc. = 1h), com x variando entre 0 e 1 mudado em intervalos de 0,1. O estudo cinético foi executado registrando-se curvas corrente-potencial e pela determinação da ordem de reação com respeito aos íons H + e Cl -. Um valor constante do coeficiente de Tafel de 33 mV foi obtido para concentrações de RuO 2 entre 0-80% mol, aumentando para 40 mV para concentrações superiores de RuO 2 . Os dados experimentais apoiam o mecanismo de Erenburg e cols. para a RDCl. Um único mecanismo explica os resultados experimentais assumindo que o efeito "edge" influencie os valores do coeficiente de transferência eletrônica. A análise da atividade eletrocatalítica mostra que misturas de óxidos aumentam a atividade eletrocatalítica aparente.A systematic investigation of the mechanistic and electrocatalytic properties of the chlorine evolution reaction, ClER, on mixed rutile/spinel oxides of nominal composition Ti/ [RuO 2 (x)+Co 3 O 4 (1-x)] was done. Electrodes were prepared using the thermal decomposition procedure (T calc. = 470 o C; t calc. = 1h), with x varied between 0 and 1, changed in 0.1 steps. Kinetics were studied recording quasi-stationary current-potential curves and reaction order determined with respect to H + and Cl -. A constant Tafel slope of about 33 mV was found for the 0 -80 mol% RuO 2 concentration interval, increasing to 40 mV for higher RuO 2 contents. Experimental data support the mechanism originally proposed by Erenburg et al. for the ClER. The edge effect exerts an influence on the electronic transfer coefficient values. Analysis of the electrocatalytic activity reveals an increase in the apparent electrocatalytic activity for the mixed oxides.Keywords: cobalt, ruthenium, chlorine evolution, electrocatalytic activity IntroductionInvestigations of the chlorine evolution reaction, ClER, reveal this reaction is an "easy" one (low overpotential) characterised by a close to theoretical Tafel coefficient (30-40 mV). [1][2][3][4] Normally the ClER does not show a significant dependence on the nature of the electrode material. 1 However, the electrode kinetics can present a dependence on such parameters as the electrode morphology (e.g. roughness, porosity) and the electrolyte pH. 5 The ClER is thermodynamically unfavoured (E o = 1.36V(vs. RHE)) compared to the oxygen evolution reaction, OER, (E o = 1.23V(vs. RHE)). However, chlorine can be produced from aqueous solutions with high current efficiency, especially at the lower pH-values of the electrolyte, due to the significant overpotential displayed by most electrode materials for the OER. 6 However, OER remains a side reaction during chlorine evolution, affecting directly the purity of the Cl 2 produced. 6,7 So, electrode selectivity for the ClER re...

show abstract

Section: Voltammetric Curvessupporting

confidence: 93%

supporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Chlorine evolution reaction at Ti/(RuO2+Co3O4) electrodes

Silva¹,

Boodts²,

Faria³

2003

J. Braz. Chem. Soc.

View full text Add to dashboard Cite

show abstract

“…All components were modified separately: (i) TiO 2 was thermally treated at 480 • C, (ii) multiwalled carbon Catalysts surface area was determined trough double layer capacity, measured by cyclic voltammetry [18,19]. The ratio of real versus geometric surface area of the electrodes can be determined as a quotient of catalyst's double layer capacity C dl versus double layer capacity C dlo of pure oxide surface.…”

Section: Methodsmentioning

confidence: 99%

Study of structural and electrochemical characteristics of Co-based hypo–hyper d-electrocatalysts for hydrogen evolution

Paunović¹,

Popovski²,

Dimitrov³

et al. 2007

Electrochimica Acta

View full text Add to dashboard Cite

Structural and electrochemical characteristics of hypo-hyper d-electrocatalytic materials aimed for preparation of electrodes for hydrogen evolution were studied. The basic catalytic material was prepared of 10% amorphous Co (grain size <2 nm), 18% amorphous TiO 2 and Vulcan XC-72, by sol-gel procedure. A number of modifications were applied aimed at improving the materials performances: (i) TiO 2 was transformed into anatase by heating at 480 • C for 1 h, (ii) multiwalled carbon nanotubes (MWCNT) were used as a catalyst support instead of Vulcan XC-72 and (iii) Mo was added to Co phase in a quantity of 25 at.% (Mo:Co = 1:3).Both, material's intrinsic catalytic activity and surface area were affected by these modifications. As a result, the electrocatalytic activity for hydrogen evolution was improved, e.g. transformation of TiO 2 into anatase form lowers the HER overpotential (η) for 15 mV at 60 mA cm −2 . Introduction of MWCNTs lowered η for 30 mV, while addition of Mo to metallic phase for 40 mV.The complete modification of all three catalyst's components (10% MoCo 3 + 18% anatase + MWCNTs) was the most effective with 60 mV decrease of overpotential.Characterization was made by XRD, SEM, IR and XPS methods. Surface area was measured by means of cyclic voltammetry.

show abstract

“…14,21,24,25 Portanto, perfis j vs. E no domínio pseudocapacitivo (1,025-1,121 V) foram registrados em função da velocidade de varredura do potencial, n, para os diferentes eletrodos.…”

Section: Caracterização Dos Filmes De óXidosunclassified

Influência das condições de resfriamento sobre as propriedades superficiais e eletroquímicas de anodos dimensionalmente estáveis

Rufino¹,

Faria²,

Silva³

2011

Quím. Nova

View full text Add to dashboard Cite

0.7 ) O 2 were studied as a function of the annealing temperature using different conditions in order to perform the cooling process of the oxide films (conventional thermal shock and the slow cooling processes). It was found that surface and electrochemical properties for the oxygen evolution reaction are both affected through the cooling process, being the electrode prepared at 400 o C using the slow cooling process the less susceptible to wear. The Tafel slope obtained in the high overpotential domain was analysed in light of the apparent charge transfer coefficient.Keywords: slow cooling treatment; morphology factor; apparent charge transfer coefficient. INTRODUÇÃOO sistema eletródico binário Ti/(Ru+Ti)O 2 constitui um dos principais tipos de anodos dimensionalmente estáveis, ADE.1-4 Além da produção de cloro, 5 os ADE também podem ser utilizados em diferentes processos, como é o caso da remoção de poluentes orgânicos recalcitrantes presentes em efluentes aquosos. 6Diferentes métodos já foram propostos para o preparo de eletrodos do tipo ADE. [7][8][9] No entanto, se verifica que o método mais utilizado nos processos industriais é baseado no preparo de ADE policristalinos mediante a decomposição térmica da mistura dos sais precursores sobre o suporte metálico rugoso.1-4 Estudos revelam que a temperatura de decomposição (calcinação) da mistura precursora deve ser suficientemente alta para se obter a formação do filme de óxidos sem, no entanto, comprometer as propriedades mecânicas e elétricas do substrato metálico. 1,[10][11][12][13] Estudos revelam que a origem da influência do ADE sobre a velocidade dos processos eletródicos está relacionada com a presença de efeitos eletrocatalíticos verdadeiros (redução na barreira de ativação para o processo de transferência eletrônica) e aparentes, devida à influência da extensão da área eletroquimicamente ativa na eletrocatálise heterogênea. 11-16A influência da temperatura de calcinação sobre as propriedades superficiais e eletroquímicas de eletrodos do tipo ADE já foi relatada para diferentes sistemas binários e ternários. [15][16][17] No entanto, se verifica nestes casos que o processo adotado na etapa de resfriamento dos filmes é o choque térmico baseado na remoção abrupta dos filmes do forno utilizado no processo de calcinação.A influência do processo de resfriamento lento sobre as propriedades superficiais e eletrocatalíticas de sistemas binários (IrO 2 +Ta 2 O 5 e IrO 2 +Nb 2 O 5 ) foi investigada com base nas reações de desprendimento de oxigênio e ozônio, 14,18 onde se verificou que o processo de resfriamento lento pode modificar de forma considerável estas propriedades, bem como o tempo de vida útil dos eletrodos.No presente artigo relata-se o estudo comparativo das propriedades superficiais e eletroquímicas de eletrodos do tipo ADE de composição nominal Ti/(Ru 0,3 Ti 0,7 )O 2 preparados por decomposição térmica em diferentes temperaturas, onde foram empregados os processos de resfriamento rápido (choque térmico) e lento. PARTE EXPERIMENTAL Preparo dos eletro...

show abstract

Determination of the morphology factor of oxide layers

Cited by 162 publications

References 21 publications

Chlorine evolution reaction at Ti/(RuO2+Co3O4) electrodes

Chlorine evolution reaction at Ti/(RuO2+Co3O4) electrodes

Study of structural and electrochemical characteristics of Co-based hypo–hyper d-electrocatalysts for hydrogen evolution

Influência das condições de resfriamento sobre as propriedades superficiais e eletroquímicas de anodos dimensionalmente estáveis

Contact Info

Product

Resources

About