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

Abstract

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...

Highly Selective Active Chlorine Generation Electrocatalyzed by Co3O4 Nanoparticles: Mechanistic Investigation through in Situ Electrokinetic and Spectroscopic Analyses

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Unusual Ligand Assistance in Molecular Electrocatalysis via Interfacial Proton Charge Assembly

“…As mentioned before, for oxidative electrocatalysis, the oxidized Co species mediates the reaction in a complex sequence of events, − and its enrichment in the TCCoPc in an acidic medium (Figure ) explains the higher activity of this electrocatalyst over the other. Further, the Tafel slope values on these electrocatalysts indicate a Volmer–Heyrovsky mechanism as explained before.…”

Espectroscopia de impedância eletroquímica aplicada ao estudo das reações heterogêneas em ânodos dimensionalmente estáveis

“…As propriedades mecânicas, elétricas e catalíticas dos ADEs são de grande interesse científico e muitas questões relacionadas aos mesmos requerem um entendimento mais aprofundando. Sendo assim, tem-se um número elevado de trabalhos abordando estudos cinéticos e as aplicações destes eletrodos em reações de oxidação de cloro (RDCl) 24,39,41 , oxigênio (RDO) 13,36,38,40,45,47,48,51,53 e oxidação de moléculas orgânicas 15,44,60,66,[69][70][71] .…”