This thesis focused on iron-based Fischer-Tropsch catalysts. It deals with different iron phases that might play a role in the catalytic process. As the activation step takes place inside the reactor (in-situ at high temperature and pressure), studying the catalyst activation process is not trivial. In addition, since the working catalysts are air sensitive, also post analysis on activated and used catalysts is challenging. As a result, the identity of the real active phase is still unknown.

To gain more insight in Fischer-Tropsch catalysts, we used different techniques like (in-situ) TEM, TEM-EELS, ED and PXRD. TEM and ED are very suitable techniques since they provide very high spatial resolutions (in the Å range). Special TEM grids and TEM holders were designed for this research in order to mimic the activation conditions and / or avoid any exposure to air.

Our results indeed showed that it is essential to avoid any exposure to air prior to analysis. In fact, we can question the results of some older publications where catalysts were exposed. In contrast to literature data published so far, we found no carbon deposits on the outer rim of the iron carbides at high temperature conditions. Overall, we showed that carbon surface layers can change, or even form, during exposure to air. We also found evidence for what in the literature has been designated as “hypothetical q¥-Fe2C”. We proposed a structure model for which the carbon content is higher than in the pure c-Fe5C2 carbide. More research is required to elucidate the exact nature of working iron-based Fischer-Tropsch catalysts.

With the focus in automobile industry to switch from petroleum-based vehicles to all electric vehicles, the increasing demand on harvesting energy from renewable sources for a safer and greener future and the ever-increasing demand of the portable electronics systems, the need for better batteries is eminent. The ultimate aim of battery research is to develop a low cost, light and small battery that can deliver high-capacity and/or high power. Lithium and sodium batteries are the frontrunners in achieving this ultimate battery. A macro battery is composed of thousands of millions of nanoparticles. Thus, to prepare a better battery we must determine the respective effects of electrode nanoparticle size, shape, structure, grain–grain boundary, defects and doping on the battery performance. To do so electrode nanoparticles need to be probed at the nano-scale to find out the correlation between their morphology, structure and chemical properties and their evolution due to the battery charging-discharging with battery performance. In this thesis we have utilized the unique capability of electron microscope to resolve the microstructural and chemical information at the (sub)nanometer scale to probe the electrode nanoparticles for making better batteries.