Cyclic voltammetric behaviour of dimensionally stable anodes in the presence of C1 - C3 aldehydes

Malpass, Geoffroy Roger Pointer; Motheo, Artur J.

doi:10.1590/s0103-50532003000400023

Cited by 9 publications

(9 citation statements)

References 11 publications

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“…Similar results have also been found by Hu [20]. However, at low temperature we found (101) is preferred, which is different to Hu's results.…”

Section: Resultssupporting

confidence: 70%

“…Combining this with temperature dependent preferable crystallite orientation, (101) IrO 2 crystallites formed at either low or moderate temperature might be less stressed and/or less influenced by dissolved Ta atoms. It has been reported that (101) rutile IrO 2 displays better catalytic activity since the length of the bond for Ir-O is shorter for (101) than the other facets [20]. It also has been reported that the stability of (101) IrO 2 crystallites for OER is better than (110) IrO 2 [11].…”

Section: Resultsmentioning

confidence: 99%

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Electrochemical Behaviour of Industrial IrO₂-Ta₂O₅Anodes for Copper Electrowinning

Haarberg

Sunde

et al. 2017

ECS Trans.

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In this work, industrial IrO 2 -Ta 2 O 5 anodes calcined at different temperatures were investigated. The results show that the calcination temperature has significant influence on the surface microstructure including the crystallinity and the preferred orientation of IrO 2 crystallite of the formed IrO 2 -Ta 2 O 5 binary oxide. The IrO 2 phase is partially amorphous at low calcination temperature in the present study. The (101) IrO 2 planes dominate at low or moderate calcination temperatures, whereas the (110) IrO 2 orientation was preferred at the highest calcination temperature.Surface morphology of the anodes was revealed as mud-cracks surrounded by a flat area with plenty of scattered nano-IrO 2 crystallites. The size of the nano-IrO 2 crystallites is calcination temperature dependent, which in turn determines the electrochemical active surface area (ECSA). In this IrO 2 -Ta 2 O 5 binary oxides coating, (101) IrO 2 was found to have higher catalytic activity than (110) IrO 2 with respect to the oxygen evolution reaction (OER).The moderate temperature is suggested as the best calcination temperature for this certain anode regarding the ECSA, electrocatalytic activity for OER and stability potential.

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“…Similar results have also been found by Hu [20]. However, at low temperature we found (101) is preferred, which is different to Hu's results.…”

Section: Resultssupporting

confidence: 70%

Section: Resultsmentioning

confidence: 99%

Electrochemical Behaviour of Industrial IrO₂-Ta₂O₅Anodes for Copper Electrowinning

Haarberg

Sunde

et al. 2017

ECS Trans.

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“…The displayed broad peaks between the OER and the hydrogen evolution correspond to oxidation state transitions of noble metals (Ir 3+ /Ir 4+ in this case). 30 It is clear that the peak current decreases with increasing calcination temperature and moves the onset potential of OER toward more positive potentials. Since the oxide compositions are almost equal, an apparent change in voltammetric response and OER onset potential may be attributed to the surface morphology and a change in active surface area.…”

Section: Resultsmentioning

confidence: 95%

Calcination Temperature Dependent Catalytic Activity and Stability of IrO₂–Ta₂O₅Anodes for Oxygen Evolution Reaction in Aqueous Sulfate Electrolytes

Haarberg

Sunde

et al. 2017

J. Electrochem. Soc.

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In this work, commercial IrO 2 -Ta 2 O 5 anodes with a certain composition calcined at three different temperatures were investigated. The results show that the calcination temperature has a significant influence on the electrocatalytic activity for the oxygen evolution reaction (OER). This is attributed to the influence of the calcination temperature on the surface microstructure including the crystallinity and the preferred orientation of IrO 2 crystallites of the IrO 2 -Ta 2 O 5 binary oxide formed. The surface morphology of the anodes was revealed as mud-cracks surrounded by flat areas containing several scattered IrO 2 nanocrystallites. The size of these nanocrystallites, which in turn contribute to the electrochemical active surface area, is dependent on calcination temperature. The (101)-surfaces of the IrO 2 were found to have higher catalytic activity than (110) IrO 2 with respect to the OER. The (101) IrO 2 planes were dominating at low or moderate calcination temperatures, whereas the (110) IrO 2 orientation was preferred at the highest calcination temperature. Accelerated lifetime tests of the investigated samples indicate that the (101) IrO 2 is more stable (110) IrO 2 during electrolysis. A moderate temperature is suggested as the best calcination temperature for this type of anode regarding the electrochemical active surface area, electrocatalytic activity and stability for OER in acidic aqueous electrolytes at operating conditions. © The Author Efficient electrowinning (EW) in aqueous sulfate electrolytes depends on fast reaction kinetics, low ohmic resistances and suppression of parasitic and detrimental reactions. The overall cell voltage is determined by the thermodynamic potentials for metal deposition (cathode) and oxygen evolution (anode), in addition to overpotentials and ohmic voltage drops. The sluggish reaction kinetics of the oxygen evolution reaction (OER) in low-pH sulfate electrolytes lead to rather high anode overpotential at industrial relevant current densities, thus being a significant contributor to an increased cell voltage.1 The low pH, moderate temperature and high anode potential in aqueous metal electrowinning limit the anode material selection significantly, as few materials are stable at these operating conditions. Therefore, identifying an efficient anode catalyst to facilitate the OER by lowering the overpotential has been considered an important research field over many decades also in copper EW.2,3 From an industrial perspective, stability and service lifetime of the anodes are just as important as the electrocatalytic activity. Ru oxide catalysts are known to be the most active for OER, 4 but not stable enough for long term operation in the acidic environment.5 IrO 2 is also very active toward OER and significantly more stable than RuO 2 , but also suffers from some degradation during prolonged operation. [6][7][8][9] Comninellis and Vercesi performed a comprehensive study of nine different binary catalyst coatings.10 They reported that the 70 mol% IrO 2 -30 mol% Ta...

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“…3,8,9 This is exemplified by an increase in the value of the anodic charge in the potential region above 0.5 V vs. MSE and an increase in the current associated with the oxygen evolution reaction (OER). The effect of increasing the concentration of formaldehyde is manifested by a quasi-linear increase in the magnitude of q fN for all electrodes.…”

Section: Cyclic Voltammetry In Presence Of Formaldehydementioning

confidence: 99%

“…3,8 Two different concentrations were investigated, one in the higher concentration domain (0.10 mol dm -3 ) and the other in the lower range (0.01 mol dm -3 ), in order to compare the results obtained in the previous section.…”

Section: Galvanostatic Electrolysismentioning

confidence: 99%

Screening process for activity determination of conductive oxide electrodes for organic oxidation

Malpass

Motheo

2008

J. Braz. Chem. Soc.

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Um método modificado para o cálculo da carga faradaica normalizada (q fN ) é proposto. O método envolve a simulação de um processo de oxidação, por voltametria cíclica, empregando potenciais na região da reação de desprendimento de oxigênio (RDO). Este método é aplicável a espécies orgânicas, cuja oxidação não é manifestada por um pico de oxidação definido em eletrodos de óxidos condutores. A variação de q fN para eletrodos de composição nominal Ti/Ru X Sn 1-X O 2 (x = 0,3; 0,2 e 0,1), Ti/Ir 0,3 Ti 0,7 O 2 e Ti/Ru 0,3 Ti 0,7 O 2 , na presença de diferentes concentrações de formaldeído foi investigada. Foi observado que eletrodos contendo SnO 2 são os mais ativos frente à oxidação de formaldeído. Subseqüentemente, para investigar a aplicabilidade do modelo proposto, eletrólises galvanostáticas (40 mA cm -2 ) de formaldeído foram efetuadas em duas concentrações distintas (0,10 e 0,01 mol dm -3 ). Os resultados estão de acordo com o modelo proposto e indicam que este novo método pode ser usado para determinar a atividade relativa de eletrodos de óxido. De acordo com trabalhos prévios, pode ser concluído que não somente a natureza do material eletródico, mas também a espécie orgânica em solução e a sua concentração são fatores importantes a serem considerados na oxidação de espécies orgânicas.A modified method for the calculation of the normalized faradaic charge (q fN ) is proposed. The method involves the simulation of an oxidation process, by cyclic voltammetry, by employing potentials in the oxygen evolution reaction region. The method is applicable to organic species whose oxidation is not manifested by a defined oxidation peak at conductive oxide electrodes. The variation of q fN for electrodes of nominal composition Ti/Ru X Sn 1-X O 2 (x = 0.3, 0.2 and 0.1), Ti/Ir 0.3 Ti 0.7 O 2 and Ti/Ru 0.3 Ti 0.7 O 2 in the presence of various concentrations of formaldehyde was analyzed. It was observed that electrodes containing SnO 2 are the most active for formaldehyde oxidation. Subsequently, in order to test the validity of the proposed model, galvanostatic electrolyses (40 mA cm -2 ) of two different formaldehyde concentrations (0.10 and 0.01 mol dm -3 ) were performed. The results are in agreement with the proposed model and indicate that this new method can be used to determine the relative activity of conductive oxide electrodes. In agreement with previous studies, it can be concluded that not only the nature of the electrode material, but also the organic species in solution and its concentration are important factors to be considered in the oxidation of organic compounds.

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Cyclic voltammetric behaviour of dimensionally stable anodes in the presence of C1 - C3 aldehydes

Cited by 9 publications

References 11 publications

Electrochemical Behaviour of Industrial IrO₂-Ta₂O₅Anodes for Copper Electrowinning

Electrochemical Behaviour of Industrial IrO₂-Ta₂O₅Anodes for Copper Electrowinning

Calcination Temperature Dependent Catalytic Activity and Stability of IrO₂–Ta₂O₅Anodes for Oxygen Evolution Reaction in Aqueous Sulfate Electrolytes

Screening process for activity determination of conductive oxide electrodes for organic oxidation

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Cyclic voltammetric behaviour of dimensionally stable anodes in the presence of C1 - C3 aldehydes

Cited by 9 publications

References 11 publications

Electrochemical Behaviour of Industrial IrO2-Ta2O5Anodes for Copper Electrowinning

Electrochemical Behaviour of Industrial IrO2-Ta2O5Anodes for Copper Electrowinning

Calcination Temperature Dependent Catalytic Activity and Stability of IrO2–Ta2O5Anodes for Oxygen Evolution Reaction in Aqueous Sulfate Electrolytes

Screening process for activity determination of conductive oxide electrodes for organic oxidation

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Product

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Electrochemical Behaviour of Industrial IrO₂-Ta₂O₅Anodes for Copper Electrowinning

Electrochemical Behaviour of Industrial IrO₂-Ta₂O₅Anodes for Copper Electrowinning

Calcination Temperature Dependent Catalytic Activity and Stability of IrO₂–Ta₂O₅Anodes for Oxygen Evolution Reaction in Aqueous Sulfate Electrolytes