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SUSTAINABLE ENERGY CONVERSION
With global efforts for carbon neutrality, establishment of sustainable energy cycles including production of renewable electricity and energy conversion into useful chemicals gains immediate attention. In this regard, it is crucial to design novel catalysts that exhibit high performance in target electrocatalytic reactions, such as hydrogen evolution reaction (HER), oxygen reduction reaction (ORR) and CO2 reduction reaction (CO2RR).
Our research focuses on understanding fundamental mechanisms governing the catalytic interfacial reaction, activation, and degradation processes. By monitoring of physicochemical changes with in situ techniques combined with TEM, XRD and Raman spectroscopy, we directly monitor structural changes of catalysts during electrochemical reactions.
e-LCTEM for Electrochemical Catalysts
In situ electrochemical liquid-cell TEM (e-LCTEM) is a powerful tool to observe dynamic behavior of catalysts during potential cycling in the single particle level. Our research aims to develop a reliable and reproducible in situ e-LCTEM platform by selective catalyst loading on the working electrode of e-LCTEM chip. This platform allows direct observation of structural changes in individual catalysts under realistic operating conditions. By combining e-LCTEM with ensemble-scale analytical tools such as XRD and Raman spectroscopy, we elucidate fundamental mechanisms involved in various catalytic reactions and degradation mechanisms of catalytic materials and aim for systematical design of novel catalysts with high performance.
Proton Exchange Membrane Fuel Cell Catalysts
The corrosive environment and high positive potential at the cathode side of the proton exchange membrane fuel cell (PEMFC) tend to deteriorate the activity of the cathode catalyst, limiting the lifespan of the PEMFC. Understanding the structural degradation of both the catalytically-active Pt-based nanoparticles and supports during cell operation provides insights into designing stable cathode catalysts. Our research goal is to investigate the degradation process of catalysts in multiple length scales, from the nanometer-scale to the atomic-scale. Identical location transmission electron microscopy (IL-TEM) in combination with rotating ring disk electrode (RRDE) techniques enable us to elucidate the structural changes of individual nanoparticles and their influence on the activity of the catalyst.
CO2 Reduction Reaction
Electrochemical CO2 reduction reaction (CO2RR) holds great potential to overcome recent global warming and climate change issues by establishing a sustainable cycle for producing value-added chemicals: utilization of water as a hydrogen/electricity source from renewable energy and/or mild reaction conditions. However, electrochemical conditions and reactants for CO2RR induce structural change in catalysts, which affect catalytic activity but are too dynamic to be characterized by classical tools. Our research targets investigating the structural dynamics of as-synthesized catalysts under CO2RR environment and finding the key structural factors for high activity via a combination of fundamental and practical approaches including in situ characterizations (in situ TEM/in situ Raman/in situ PL and etc.), ex situ characterizations (High-resolution TEM/STEM, XPS, EPR and etc.), as well as catalytic performance tests. Based on the findings, we develop promising heterogeneous catalysts for CO2RR and propose a research platform for designing new active sites toward sustainable reactions.
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