Dr. Gerold Willing
Department of Chemical Engineering
University of Louisville
Louisville, KY 40292
Phone: 502-852-7860
E-mail: gerold.willing@louisville.edu
Photoelectrochemical Cells (PECs) show great potential as a highly efficient platform for direct solar power generation. PECs are composed of an organo-metallic photosensitive dye physisorbed onto a metal oxide framework that is attached to the working electrode of an electrochemical cell. Charges that are produced when photons strike the dye molecules must cross several different interfaces before they can be utilized as current carriers. As such, it is easy to understand that improving the mobility of these charges across the dye/metal oxide or metal oxide/electrode interface will directly impact the overall efficiency of a PEC.
In this work, we will investigate the electron transport at the nanoscale in metal oxide nanowire and nanoparticle based PECs by using an electrochemical potentiostat connected to an atomic force microscope, a so called Electrochemical AFM (EC-AFM), to study the topography of the nanowires and the electrochemical behavior of the dye molecule/metal oxide electrode. The influence of the interfacial interactions on electron transfer within the metal oxide matrix and its effect on the efficiency of the PEC will be directly measured on the nanoscale using the AFM tip as the counter electrode. In this configuration, the EC-AFM will not only be able to determine where on the metal oxide electrode one observes the highest rates of electron transfer, but it will also be able to directly probe the current and voltage (I-V) characteristics of those regions with a lateral resolution of 10 nm. Additionally, by performing electrochemical impedance spectroscopy (EIS) measurements over these same regions, we will begin to develop a clearer understanding of the role of interfacial resistance in PEC efficiency. Based on these measurements, development of appropriate strategies for enhancing the binding and electron transfer across the dye/metal oxide interface can begin. With appropriate engineering and optimization of this interface, one can expect both an enhancement in the efficiency of current PECs due to the increased electron transfer, but also an increased life span due to the greater degree of binding between the dye and the metal oxide surface.
mehanna@engr.uky.edu