The utilization of templated porous electrodes in electrochemical applications

Abstract

The unifying theme within this work is three-dimensionally ordered macroporous (3DOM) carbon. This material consists of an ordered array of pores surrounded by a skeleton of amorphous carbon with nanometer-scale dimensions. 3DOM carbon offers several advantages that make it ideal for use in electrochemical applications. It has a high surface area, an interconnected pore structure, it is electrically conductive and chemically inert, the surface chemistry can be modified and characterized using slight modifications of well-established techniques, and robust monoliths can be produced. Here, 3DOM carbon was utilized in three distinct electrochemical applications. A three-dimensional interpenetrating lithium ion battery with a 3DOM carbon anode and a mixed vanadia/ruthenia cathode was investigated. Optimization of the synthesis of the polymeric separator layer and the ruthenia component of the cathode were carried out. The synthesis conditions and post-synthesis treatment greatly affect the degree of ruthenia deposition within the porous structure and the extent of hydration of the product. An ion-selective electrode system with 3DOM carbon as the solid contact was developed. 3DOM carbon was covered with an ionophore-based sensing membrane, allowing for selective detection of K<super>+</super> or Ag<super>+</super>. This system exhibited very low detection limits (4.3 ppt for Ag<super>+</super>), unprecedented electrode stability, and little-to-no response to common interferents (such as carbon dioxide and light). The reasons for this excellent performance were investigated using a variety of characterization methods (with an emphasis on electrochemical techniques). The high surface area and low concentration of surface functional groups on 3DOM carbon are important factors. A receptor-based sensor for explosives detection was also developed. The pore walls of 3DOM carbon were modified with a receptor for 2,4-dinitrotoluene (DNT) using a series of chemical and electrochemical modification steps. Only 3DOM carbon that had been modified with the receptor exhibited a response to the presence of DNT. This selective detection of DNT was also possible in the presence of interfering molecules. However, the high capacitance of the 3DOM carbon led to poor limits when using cyclic voltammetry as the detection method. When square wave voltammetry was used, which eliminates the capacitive currents, much improved detection limits (10 &mu;M) were achieved.