Spray-flame-synthesized LaCo1–xFexO3±δ perovskites for electrocatalysis

This dissertation is based on experiments to research the potential of spray-flame-synthesized LaCo1̶ xFexO3 perovskite as non-precious-metal based electrocatalysts towards OER and EtOR.</br> These complex oxide perovskites were successfully synthesized before by numerous synthesis techniques such as the Pechini sol-gel method, co-precipitation, and reactive grinding; and Co- and Fe-based perovskites were put forward as highly active OER catalyst in numerous studies.</br> However, few research studies were oriented to develop methods to produce high-surface area, nanosized perovskite catalysts that could be used in large-scale production. Therefore, the rationale behind this research is to show that spray-flame synthesis can be the suitable technique to produce high-surface area perovskite nanoparticles as electrocatalysts in a continuous scalable process.</br> A series of LaCo1–xFexO3 nanoparticles with different Fe contents were synthesized by spray-flame synthesis by varying process parameters and precursor solution compositions. With the aid of heat-treatment of the as-synthesized nanoparticles in O2, the physical properties of the as-synthesized nanoparticles were further modified.</br> Comparative analyses on the bulk, surface, morphological, and magnetic properties of the perovskites were performed to determine the influence of Fe substitution on the OER catalytic activity.</br> All experiments and analyses are a result of the collaborative research study of several research groups; namely, the synthesis and materials characterizations by the author in collaboration with the Interdisciplinary Center for Analytics on the Nanoscale (ICAN) and the Wende group in the University of Duisburg-Essen Electrocatalytic and operando electrochemistry investigations were performed in the Schuhmann and Muhler Groups at the Ruhruniversität Bochum.</br> Based on this collaborative effort, spray-flame synthesis, nanoparticle characterization, and the investigation of the OER and EtOR catalytic activity of Fe-substituted LaCoO3 nanoparticles was combined with operando electrochemistry/ATR-FTIR measurements giving insight into the influence of Fe substitution on electrochemical properties of LaCoO3.</br> The focus of this work is on optimizing spray-flame synthesis parameters and heat treatment processes for improving the stoichiometric perovskite phase content while decreasing carbon contamination.</br> Overall, the synthesis and analyses methodology applied for the specific mate-rials system of LaCo1–xFexO3 perovskites in this dissertation, was intended to be made useful for a wide range of other spray-flame made perovskites and complex oxide nanoparticles for electrocatalytic and other catalytic applications.



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