(Invited) Electrolytic Metal Atoms Enabled Manufacturing of Nanoporous Structures

Abstract

Nanostructuring surface layers of a metallic electrode is of particular interest for a wide range of potential applications because the nanostructures can not only increase the active area accessible to liquid or gaseous media and reactants but also improve electron mobility in the solid ligaments. In the past two decades, several strategies have been developed to design and fabricate nanostructured electrodes with highly ordered networks and high surface area [1]. Template synthesis is a popular approach for preparing nanoporous metals ranging from microporous to macroporous, and further to hierarchical porous structures. The control over the nanostructures enables systematically experimental and theoretical studies of the electrode structure-activity relationship. Despite the great success of the template syntheses, they are limited to producing nanoporous thin films or macroparticles with irregular morphologies. Since the shape and size distribution of nanostructures are critical parameters of their function and utility for specific applications, the preparation of porous metal nanostructures with a well-defined shape is highly desirable and technologically important. For this purpose, surfactant mediated synthesis has received considerable attention in the fabrication of nanoporous metal structures. A seeding reduction method has been developed to synthesize nanoporous platinum and other metals. The nanoporous structures exhibit remarkable surfactant-dependent morphological properties. The above techniques provide a formidable toolkit for nanostructuring electrode materials and have been dramatically utilized in the manufacturing of electrochemical systems. However, the high cost of the manufacturing of nanostructures is still a barrier to their commercial implementation into the advanced systems. The cost-reduction of the manufacturing techniques is one crucial target for continued research.For the above purposes, a unique electrochemical method based on one-pot electrochemical deposition and dissolution of metal atoms onto a target electrode substrate is a front-runner technology. Based on this method, metal atoms deposit from their corresponding metal ions and are directed to “attack” the substrate electrode in the electrodeposition mode, and they are removed from the substrate in the subsequent electro-dissolution mode. Moreover, the electrochemical deposition and dissolution of metal atoms can be conveniently manipulated through simple potential modulation such as potential cycles. In principle, no net consumption of chemicals such as metal salts, can be achieved. A range of metallic and alloy electrodes have been successfully nanostructured using different electrolytic metal atoms by this method [2, 3]. Some of them have demonstrated impressive performance for several different application in electrocatalysis, energy storage, and sensors.In this presentation, we will introduce the thermodynamic and kinetic fundamentals of this manufacturing technique, the characterization of resulting nanostructures, the analysis of their electrochemical behavior, the implementation of this technique for the development of advanced electrodes, and a preliminary economic analysis of this technique.