The dual pathway in action: decoupling parallel routes for CO2 production during the oscillatory electro-oxidation of methanol

Nagao, Raphael; Cantane, Daniel A.; Lima, Fabio H. B.; Varela, Hamilton

doi:10.1039/c2cp00037g

Cited by 68 publications

(98 citation statements)

References 37 publications

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“…The multipeaked structure observed in the production of carbon dioxide (c.f. features i−iii in Figure 5c), was uncovered by Nagao et al 32,33 by means of experiments, modeling and simulations. In short, the authors assigned peaks i to the electro-oxidation of adsorbed carbon monoxide, and peaks ii and iii to the, non-CO, direct pathway.…”

Section: ■ Results and Discussionmentioning

confidence: 94%

Production of Volatile Species during the Oscillatory Electro-oxidation of Small Organic Molecules

et al. 2014

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The study of complex reaction under oscillatory conditions has been proven to be useful in uncovering features that are hidden under close to equilibrium regime. In particular, for the electro-oxidation of small organic molecules on platinum and platinum-based surfaces, such investigations have provided valuable mechanistic information, otherwise unavailable under nonoscillatory conditions. We present here the dynamics of production of volatile species along the oscillatory electro-oxidation of formic acid, methanol, and ethanol on platinum, as measured by online differential electrochemical mass spectrometry (DEMS). Besides the presentation of previously unreported DEMS results on the oscillatory dynamics of such systems, we introduce the use of multivariate linear regression to compare the estimated total faradaic current with the one comprising the production of volatile species, namely: carbon dioxide for formic acid, carbon dioxide and methylformate for methanol, and carbon dioxide and acetaldehyde for ethanol. The introduced analysis provided the best combination of the DEMS ion currents to represent the total faradaic current, or, equivalently, the maximum possible faradaic contribution of the volatile products for the global current. The mismatch between estimated total current and the one obtained by the best combination of partial currents of volatile products was found to be small for formic acid, 4 and 5 times bigger for ethanol and methanol, respectively, evidencing the increasing role played by partially oxidized, soluble species in each case. These results were discussed in connection with the mechanistic aspects of each system. Moreover, we have defined some descriptors to account for the production of volatile species, and discussed dynamics in terms of sample and populational covariances

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Section: ■ Results and Discussionmentioning

confidence: 94%

Production of Volatile Species during the Oscillatory Electro-oxidation of Small Organic Molecules

et al. 2014

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“…The oscillatory activation energy, E ω , was estimated with the temperature effect on the oscillation frequency [53] and in terms of the normalized applied current [8,23,26]. As the oscillatory system was found to spontaneously evolve in time.…”

Section: Resultsmentioning

confidence: 99%

“…Examples of this phenomenon have been reported during the electro-oxidation of formic acid [6,7,8,9,10,11,12], formaldehyde [11,13,14,15], methanol [14,16,17,18], ethanol [19], ethylene glycol [20,21] and glycerol [22] in both acid and alkaline media (reference [21] provides a deeper description). Interestingly, the electro-oxidation under oscillatory regime can reveal unique features and even contribute to elucidate some mechanistic aspects, as for instance: the temperature (over)compensation phenomenon during the electro-oxidation of formic acid [8] [6]; the possibility of decoupling the parallel pathways [18,23] and, the direct estimation of kinetic parameter [24,25,26]. …”

Section: Introductionmentioning

confidence: 99%

The Electro-Oxidation of Ethylene Glycol on Platinum over a Wide pH Range: Oscillations and Temperature Effects

2013

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We report a comprehensive study of the electro-oxidation of ethylene glycol (EG) on platinum with emphasis on the effects exerted by the electrolyte pH, the EG concentration, and temperature, under both regular and oscillatory conditions. We extracted and discussed parameters such as voltammetric activity, reaction orders (with respect to [EG]), oscillation’s amplitude, frequency and waveform, and the evolution of the mean electrode potential at six pH values from 0 to 14. In addition, we obtained the apparent activation energies under several different conditions. Overall, we observed that increasing the electrolyte pH results in a discontinuous transition in most properties studied under both voltammetric and oscillatory regimes. As a relevant result in this direction, we found that the increase in the reaction order with pH is mediated by a minimum (~ 0) at pH = 12. Furthermore, the solution pH strongly affects all features investigated, c.f. the considerable increase in the oscillatory frequency and the decrease in the, oscillatory, activation energy as the pH increase. We suggest that adsorbed CO is probably the main surface-blocking species at low pH, and its absence at high pH is likely to be the main reason behind the differences observed. The size of the parameter region investigated and the amount of comparable parameters and properties presented in this study, as well as the discussion that followed illustrate the strategy of combining investigations under conventional and oscillatory regimes of electrocatalytic systems.

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“…Thus TFMSA could be acting on this parameter inhibiting specific sites by adsorption. Recently the distribution of soluble products was also found to be important for the understanding of oscillatory reactions and the anion could affect, through site blockage, that quantity as well [65].…”

Section: Resultsmentioning

confidence: 99%

Experimental Assessment of the Sensitiveness of an Electrochemical Oscillator towards Chemical Perturbations

2012

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In this study we address the problem of the response of a (electro)chemical oscillator towards chemical perturbations of different magnitudes. The chemical perturbation was achieved by addition of distinct amounts of trifluoromethanesulfonate (TFMSA), a rather stable and non-specifically adsorbing anion, and the system under investigation was the methanol electro-oxidation reaction under both stationary and oscillatory regimes. Increasing the anion concentration resulted in a decrease in the reaction rates of methanol oxidation and a general decrease in the parameter window where oscillations occurred. Furthermore, the addition of TFMSA was found to decrease the induction period and the total duration of oscillations. The mechanism underlying these observations was derived mathematically and revealed that inhibition in the methanol oxidation through blockage of active sites was found to further accelerate the intrinsic non-stationarity of the unperturbed system. Altogether, the presented results are among the few concerning the experimental assessment of the sensitiveness of an oscillator towards chemical perturbations. The universal nature of the complex chemical oscillator investigated here might be used for reference when studying the dynamics of other less accessible perturbed networks of (bio)chemical reactions.

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The dual pathway in action: decoupling parallel routes for CO2 production during the oscillatory electro-oxidation of methanol

Cited by 68 publications

References 37 publications

Production of Volatile Species during the Oscillatory Electro-oxidation of Small Organic Molecules

Production of Volatile Species during the Oscillatory Electro-oxidation of Small Organic Molecules

The Electro-Oxidation of Ethylene Glycol on Platinum over a Wide pH Range: Oscillations and Temperature Effects

Experimental Assessment of the Sensitiveness of an Electrochemical Oscillator towards Chemical Perturbations

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