(Invited) Interfacial Potential Distribution at Semiconductor/Liquid Interfaces: A Framework for the Quantitative Understanding of Voltammetric Data with Semiconductor (Photo)Electrodes

Abstract

This presentation will introduce a quantitative framework for interpreting and analyzing voltammetric data from semiconductor (photo)electrodes immersed in liquid electrolytes. The basis of the approach is to use the dielectric properties of the semiconductor, electrolyte, and interfacial layer(s) to calculate explicitly the fractional potential drops across the system that occur when a bias is applied relative to an external reference. These fractional potential drops are then used to determine the potential dependences of the forward and back charge-transfer rates between the semiconductor and redox acceptors/donors of interest. These rates, in conjunction with mass transport considerations, are used to predict voltammetric shapes from a variety of useful experimental configurations including diffusing and adsorbed redox species at either semiconductor macro- or ultramicroelectrodes. The goal of the work is to understand semiconductor voltammetric data directly rather than through the (limiting) lenses of either metal electrode responses or solid-state diodes.The presented framework assumes charge transfer occurs predominantly through the semiconductor band edges but a description of how contributions from surface states can affect the data will be discussed. In addition, this talk will also provide examples of how this framework improves the electroanalytical utility of semiconductor voltammetry to measure semiconductor surface reactions, the flat band potential, and interfacial dielectric properties.