Analysis of the use of voltammetric results as a steady state approximation to evaluate kinetic parameters of the hydrogen evolution reaction

Marozzi, C.A.; Canto, Mario Ruben; Costanza, Vicente; Chialvo, Abel C.

doi:10.1016/j.electacta.2005.05.040

Cited by 13 publications

(15 citation statements)

References 24 publications

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“…This is confirmed by the detection of solution trajectories whose qualitative characteristics are only possible for nonlinear systems (see the extensive review by Hudson and Tsotsis [21]). Simulations and experiments have shown hysteresis-like cyclic behavior, bistability, strange attractors and chaos [22]. These somehow unexpected experimental results shed insight over the theory of adsorption mechanisms, spatiotemporal patterns of catalytic electrodes, and related physical problems.…”

Section: Description Of the System The Volmer-heyrovsky-tafel Stepsmentioning

confidence: 82%

“…This methodology will let us obtain (in a range of T and S) the missing boundary conditions in order to simulate the three ODEs (9), (10), (12), referred to as HACE, but it will also represent a large numerical effort since the control system needs to solve three additional PDE equations, including the interpolation method to calculate g(S) and the method to find the roots of Equation (22). However, these computer calculations will be made off-line, that is to say, the computer effort will be made before the process is to be started.…”

Section: The Control Systemmentioning

confidence: 99%

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Minimal‐power control of hydrogen evolution reactions

Costanza¹,

Rivadeneira²

2009

Optim Control Appl Methods

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An integral approach to solve finite-horizon optimal control problems posed by set-point changes in electrochemical hydrogen reactions is developed. The methodology extends to nonlinear problems with regular, convex Hamiltonians that cannot be explicitly minimized, i.e. where the functional dependence of the H -minimal control on the state and costate variables is not known. The Lagrangian functions determining trajectory costs will not have special restrictions other than positiveness, but for simplicity the final penalty will be assumed quadratic. The answer to the problem is constructed through the solution to a coupled system of three first-order quasi-linear partial differential equations (PDEs) for the missing boundary conditions x(T ), (0) of the Hamiltonian equations, and for the final value of the control variable u(T ). The independent variables of these PDEs are the time-duration T of the process and the characteristic parameter S of the final penalty. The solution provides information on the whole (T, S)-family of control problems, which can be used not only to construct the individual optimal control strategies online, but also for global design purposes. electricity. These processes are receiving increasing attention given the recurrent crisis in oil prices, the search for clean energy sources to mitigate global warming, and the current rate of depletion of natural fuels. There exists an extensive bibliography on other fields of research applying HER equations, like in cold nuclear fusion (see [1]), or in the H 2 -decontamination and corrosion of heavy metals ([2] and references therein). As new applications of hydrogen technology are announced, interest is growing in the design, operation, and optimization of industrial devices based on HER systems.The control of fuel cells operation has begun to be studied recently, specially for non-isothermal proton exchange membrane prototypes (see [3]). In all cases dynamic non-linearities have been confirmed experimentally, which suggests that fuel cell technology would

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Section: Description Of the System The Volmer-heyrovsky-tafel Stepsmentioning

confidence: 82%

Section: The Control Systemmentioning

confidence: 99%

Minimal‐power control of hydrogen evolution reactions

Costanza¹,

Rivadeneira²

2009

Optim Control Appl Methods

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“…In the numerical results of this paper a value of s ¼ 2:21 Â 10 À4 C cm À2 will be adopted, corresponding to a standard Pt electrode (see [8]), and v e V ; v e H ; v e T : equilibrium reaction rates of each step. The nominal values for these parameters were chosen as to produce a dynamic response in the order of seconds, and at the same time to maintain both the Volmer-Heyrovsky and the Volber-Tafel reaction routes active (see [17])…”

Section: System Dynamics and Approximations The Suboptimal Control Pmentioning

confidence: 99%

Parametric uncertainty and disturbance attenuation in the suboptimal control of a non‐linear electrochemical process

Costanza

2007

Optim Control Appl Methods

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The optimal control of the hydrogen evolution reactions is attempted for the regulation and change of setpoint problems, taking into account that model parameters are uncertain and I/O signals are corrupted by noise. Bilinear approximations are constructed, and their dimension eventually increased to meet accuracy requirements with respect to the trajectories of the original plant. The current approximate model is used to evaluate the optimal feedback through integration of the Hamiltonian equations. The initial value for the costate is found by solving a state-dependent algebraic Riccati equation, and the resulting control is then suboptimal for the electrochemical process. The bilinear model allows for an optimal Kalman-Bucy filter application to reduce external noise. The filtered output is reprocessed through a non-linear observer in order to obtain a state-estimation as independent as possible from the bilinear model. Uncertainties on parameters are attenuated through an adaptive control strategy that exploits sensitivity functions in a novel fashion. The whole approach to this control problem can be applied to a fairly general class of non-linear continuous systems subject to analogous stochastic perturbations. All calculations can be handled on-line by standard ordinary differential equations integration software.

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“…Due to their practical significance, the hydrogen oxidation reaction ͑HOR͒ and its reverse, i.e., the hydrogen evolution reaction ͑HER͒, are by far the most extensively investigated of electrocatalytic reactions. [1][2][3][4][5][6][7][8] Further, despite being among the simplest of such reactions, their mechanistic and kinetic understanding is still incomplete. The significance of dual-pathway kinetics has recently been shown for the HOR on Pt electrode.…”

mentioning

confidence: 99%

“…Further, no realistic first-principles prediction of step kinetics yet exists for the hydrogen electrode reaction, although there is now great interest in ab initio predictions [9][10][11][12][13][14][15][16] as well as in their experimental validation. 5,8,12,[17][18][19][20][21][22] Were an accurate rate expression for HOR/HER in terms of its threestep kinetics available, it would not only be revealing, allowing fundamental questions to be answered, such as those posed recently by Gasteiger et al, 22 but when available, it could utilize the firstprinciples predictions of step kinetics to construct a comprehensive picture of this important and intriguing reaction system, including the elucidation of parallel pathways and the dominant steps. A thorough understanding of HOR and HER would also serve as a yardstick for understanding other electrocatalytic reactions.…”

mentioning

confidence: 99%

Kinetics of the Hydrogen Electrode Reaction

Vilekar,

Fishtik,

Datta

2010

Meet. Abstr.

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It is well recognized that the standard Butler-Volmer equation is lacking in an adequate description of the kinetics of the hydrogen electrode reaction over the complete range of potentials for the alkaline as well as the acid electrolytes. Further, it is unable to explain the asymmetry in current vs potential observed in the hydrogen evolution reaction ͑HER͒ vs the hydrogen oxidation reaction ͑HOR͒. In fact, even kinetic descriptions via two-step mechanisms ͑Volmer-Heyrovsky, Volmer-Tafel, or Heyrovsky-Tafel͒ are individually applicable only in limited potential ranges. We present an approach that provides explicit rate expressions involving kinetics of all the three steps ͑Tafel-Volmer-Heyrovsky͒ simultaneously, as well as more limiting rate expressions based on two-step pathways. The analysis is based on our recently developed graph-theoretic approach that provides accurate rate laws by exploiting the electrical analogy of the reaction network. The accuracy of the resulting rate expressions, as well as their asymmetric potential dependence, for both HOR and HER is illustrated here based on step kinetics provided in the literature for Pt catalyst in 0.5 M NaOH solution.

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Analysis of the use of voltammetric results as a steady state approximation to evaluate kinetic parameters of the hydrogen evolution reaction

Cited by 13 publications

References 24 publications

Minimal‐power control of hydrogen evolution reactions

Minimal‐power control of hydrogen evolution reactions

Parametric uncertainty and disturbance attenuation in the suboptimal control of a non‐linear electrochemical process

Kinetics of the Hydrogen Electrode Reaction

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