In-situ SAXS investigation of the evolution of hierarchical porosity of a soft carbon precursor during heat treatment

Nanoporous carbons show versatile applications in various fields, such as electrochemical energy storage (e.g. supercapacitors), gas storage, and devices for water deionization. It was shown that electrochemical energy storage devices benefit from materials with hierarchical porosity. In this study, one such hierarchically structured carbon, namely soft templated carbon (STC) was investigated. The STC material presented in this work was provided and synthesized by the Paris Lodron University Salzburg. STC synthesis is based on the self-assembly of rod-like micelles on a two-dimensional hexagonal lattice, acting as a mesopore space template, surrounded by a polymer. During calcination (i.e. a temperature treatment in an oxidizing atmosphere at about 300°C) the micelles are removed, resulting in a mesoporous polymer matrix which is subsequently carbonized and activated at temperatures > 800°C. This thesis aims to find optimized calcination parameters. This is done by time-resolved in-situ small-angle X-ray scattering (SAXS) of the STC material during calcination using synchrotron radiation. The influence of the variation of calcination temperature, time, ratio of nitrogen and oxygen in the atmosphere, and heating rate are studied. Structural changes are evaluated using multiple parameters derived from SAXS by a model-based approach. Adjusted calcination conditions are suggested for an optimized mesostructure of the resulting carbon precursor material. Additional gas adsorption analysis and thermogravimetric analysis are performed and presented in this work, contributing to a more complete understanding of the structural changes. This contributes to the improvement of the synthesis of STCs, and as a result, leads to optimized materials with application-relevant tailored pore properties.