Comprehensive First Principles Approach to Understanding the Electrochemical Interface and Applications to Energy Problems

Case Western Reserve University, Cleveland OH

Investigators

Abstract

In this research supported by the Analytical and Surface Chemistry Program, catalytic reaction mechanisms on electrode surfaces will be predicted and analyzed using a new theory developed in the Anderson lab for studying electrochemical interfaces. In the two-dimensional version of the new band theory program, the surface potential is adjusted by adding charge to the electrode and counter charge in the double layer. The double layer charge distribution is modeled by a modified Poisson-Boltzmann theory within a dielectric continuum model. The whole interfacial system is varied to charge self-consistency, yielding predictions of the Gibbs free energies as functions of structure and electrode potential. The theory, already found useful for predicting reversible potentials for forming reaction intermediates adsorbed on electrode surfaces as functions of potential, will be extended to characterizing transition state structures and activation energies during electron transfer reactions on electrode surfaces. Efficient energy conversion and energy storage will in the future depend more and more on making the best use of the Gibbs energy of chemical reactions in the form of electrical work and less and less on the enthalpy of chemical reactions in the form of heat and pressure-volume work. Catalysis is required to generate electrical work directly from fuels, whether by enzymes in biological systems or catalytic electrodes in fuel cells. It is critical to develop an understanding of electrocatalysis at the level of molecular structures and reaction mechanisms. Work toward this goal using the theory developed in the Anderson lab has begun and the research supported by the program will yield significant advancements. Two major thrusts are (i) gaining fundamental understanding of the factors that so far limit the efficiency and stability of platinum electrocatalysts in fuel cells, (ii) applying the insight gained to proposing new electrocatalysts, possibly not including platinum, that are as yet undiscovered. The results will be helpful to a broad scientific community and should speed the development of efficient portable electric power sources for transportation and mobile electronic device applications.