Strategic electrode design with 3D hierarchical nanostructures and their applications for CO2 reduction electrocatalyst and next-generation batteries

Abstract

As increasing interests of energy storage and conversion devices for portable electronics and electric vehicles, the energy devices are required to have high efficiency, high capacity, long life as well as economic efficiency. Since their performance is mostly determined by the characteristics of the electrode among all components, the studies of chemical and physical modulation of the electrode have attracted much attention to improving the performance. The nanostructured electrode realizes excellent performance that surpasses the inherent limitations of existing bulk material energy devices by providing a large specific surface area, shortening the reaction path, and improving surface catalytic activity. Among them, hierarchical nanostructures including a multi-dimensional structure in which nanostructures from 0 to 3 dimensional are fused or a multi-scale porous structure composed of pore structures of different sizes propose strategies to provide the rational structure for each application field using single or more than two phases. However, existing fabrication methods that can effectively produce 3D nanostructures have been limited to large area, reliability, resolution, and high process speed for use in energy devices. Proximity-field nanoPatterning (PnP) technology is advanced lithography capable of fabricating three-dimensional (3D) nanostructures with well-ordered pores of sub-micron size reliably based on optical set-up. Using this 3D nanopatterning technique is able to produce inch-sized nanostructures with a single exposure and the fabricated 3D nanostructures can be easily replaced with functional materials using solution casting, atomic layer deposition (ALD), electroplating for sensors, structural materials, optical devices, and energy devices. In this dissertation, a 3D nanostructured electrode is proposed using a variety of material substitution processes such as carbonization, ALD, and electroplating. The fabricated electrodes were analyzed using a scanning/transmission electron microscope (SEM, TEM) and energy dispersive spectroscopy (EDS), X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS) for chemical/physical analysis, and potentiostat for electrochemical analysis. Based on this, we propose a rational design of a 3D hierarchical nanostructured electrode for Li-ion battery, Li-air battery, and CO2 reduction electrocatalyst. These novel structures are expected to suggest a useful approach to similar electrochemical fields.