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The research program is aimed at exploring theoretical and experimental techniques for decoding complexity in electrochemical systems.

We have analyzed a skeleton model of electrochemical reduction reaction:

C de/dt = (V-e)/R – nFk(e)c
                            (1)

dc/dt = [-2 k(e) c  + 2D(c0-c)/a ] /a
                            2)

Equations (1) and (2) describe the charge and mass balances, respectively, for a reduction reaction. The essential variables are the electrode potential e and near-surface concentration of the electroactive species, c. C is double layer capacitance, A is the surface area of electrode, F is Faradaic constant, n is the number of electrons in the reaction, V is circuit potential, R is series resistance, a is Nernst diffusion layer thickness, and D and c0 are the diffusion constant and the bulk concentration of the electroactive species, respectively. k(e) is the potential dependent rate constant.

Although equations 1-2 constitute a relatively simple set of equations, analytical solutions are difficult to obtain because of the highly nonlinear dependence of rate constant k on potential. By a careful application of principle of critical simplification, we have obtained a formula for the frequency (f) of oscillatory behavior as the geometric mean of the chemical and electrical inverse time constants (fe and fc).

f=(fc fe)^1/2=[2k/(aRCA)]^1/2
                            3)

The formula was confirmed in electrochemical experiments by undergraduate student Lindsey Pelster and graduate student Mahesh Wickramasinghe. The results were presented at the 43^rd American Chemical Society Midwest Regional Meeting, Oct. 8-11, 2008, Kearney, Nebraska by the students and published in Physical Chemistry Chemical Physics. After successful undergradute research, Lindsey Pelster was admitted to the graduate school of Saint Louis University; presently she is developing biofuel cells with Prof. Shelley Minteer. 

During the summer we have applied the same formulation to electrocatalytic CO oxidation and obtained similar formula geometric mean type formula for bistability points. Plans for second year include elaborating the formula for CO oxidation and the water gas shift reaction and design of experiments for experimental confirmation.

While working on principle of critical simplification project, graduate student Mahesh Wickramasinghe made an interesting observation: the precision of electrochemical oscillations measured by phase diffusion exhibits Arrhenius type of dependence. The results were presented at 43^rd American Chemical Society Midwest Regional Meeting; a manuscript is being written now and it is expected that the results will point to the importance of not only the frequency, but also of the precision of various types of physical, chemical, and biological oscillations. Graduate student Mahesh Wickaramasinghe is in his 3^rd year now; the publication and manuscript being written prepares him well for defense of his research proposal in the Interdisciplinary and Applied Science graduate program of Saint Louis University. 

As an alternative approach to modeling, we have been developing methodologies to obtain null clines of electrochemical systems from direct measurements. Null clines in electrochemical systems are typically obtained from ordinary differential equations; for example the e nullcline is the functional form of setting the right hand side of equation 1 to zero. When time scale separation exists between the system variables, the dynamical evolution of system can be predicted using null cline information.

With 1^st  year graduate student Timea Nagy, we have tested an experimental methodology for obtaining null clines with concurrent control perturbations of circuit potential and electrode rotation rate. Numerical simulations indicate that the method outlined in the proposal is capable of providing the null cline points. Furthermore, the numerical simulations also indicate that the null-cline information can effectively predict  system's dynamics and thus holds promise for alternative modeling routes to traditional kinetics/mass transfer based approaches. Our efforts in the second year will be focused on testing the methodology with a somewhat more complicated model for H₂ oxidation and assembling and experimental setup for measuring experimental null clines. Timea Nagy research assistant was hired for Fall semester full time on PRF grant to support this research direction. She is expected to give presentations on her preliminary numerical simulations in 2010.

In first year of funding period we spent resources on expanding our experimental capabilities. We have built a rotating ring-disk electrode system with bipotentiostat and Labview based data acquisition/control system. The experimental setup was used in principle of critical simplification work and ready to be used in the null cline project. Experimental goal for second year include building a Labview RT real-time-controller with which both rotation rate and the circuit potential of the electrode can be controlled.

In the research laboratory we have been using microfluidic flow cells for investigations of multi-particle electrode interactions. We have made attempts to implement CO electrooxidation reaction on Pt band micro-electrodes in this microlfuidic setup; working with microcells as opposed to macrocells would provide a safer experiments and more flexibility in varying electrode sizes. Although primary goal of the proposal is still working with macrocells, longer term (2-5 years) experimental goal would make use of advantageous properties of microfluidic and lab-on-chip techniques.

The Petroleum Research Fund has been a valuable promoter of my academic activity. As a result of the support, for mid-tenure review I have one publication, one manuscript being written, two conference presentation, and preliminary data generated and used in submitted NSF CAREER grant. Stimulating collaboration has started with Prof. Gregory Yablonsky at Parks College of Engineering at Saint Louis University; Prof. Yablonsky is an expert in 'traditional' kinetic modeling of chemical systems. Our discussions on decoding chemical complexity are ongoing and will result in future grant submissions.  I plan to attend Gordon Research Conference on Chemical Oscillations and Dynamic Instabilities in 2010 and present the research results.