In the multicomponent material system, harnessing oxidation/reduction tendencies according to the elements enables to design unique fabrication process for the predictive synthesis. Starting from Gibbs free energy or chemical potential calculation according to process parameters (pressure, temperature) and atomic components, we can establish phase diagram and control the reaction pathway in this theoretical processing map. We apply this principle to fabricate various nanomaterials whose surface to volume ratio is extremely high and sensitive to external reaction.

By understanding thermodynamics and reaction kinetics during nucleation and growth stage, we aim to develop material fabrication platform which can control phase and structure of nanomaterials efficiently. Each metal compound, such as oxide, sulfide, nitride, carbide, shows different formation Gibbs free energy according to partial pressure and temperature. Combining this property with activity for solid solution and atomic diffusion, we can control crystal interfaces and microstructures which contain grain boundary and inter-phase boundary in the multi-phase composite materials. Not only for pure metallic species, we study various interfaces in heterogeneous materials such as metal/metal compound, metal/carbon, and metal/organic. 

ELECTROCATALYSIS

Electrochemical reactions for renewable energy conversion

With increasing demand for carbon neutral and recycling CO2 into value-added chemicals, renewable electricity-powered CO2 conversion is receiving great attention. The main focus of our group is electrochemical CO2 reduction reaction (CO2RR). CO2RR can produce hydrocarbon and oxygenates such as carbon monoxide, methane, formic acid, ethylene, ethanol. For CO2 conversion into target product, We develop heterogeneous catalysts which can steer catalytic reaction pathway by controlling binding of reaction intermediates at the surface of heterogeneous catalysts. For electrochemical catalytic reaction, we study fundamental understanding of proton-coupled electron transfer, electric double layer. We pursue value-added chemical production from the cathode (reduction) and anode (oxidation) side reactions.

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Multi-scale material designs for catalytic active sites control

For high product selectivity and catalytic activity, we apply thermodynamic-based nanomaterial fabrication techniques to develop heterogeneous catalysts. This covers metal alloy, coordinate structure, oxidation state, multiple boundary and interfaces, and sub-surface interstitial doping.

Electrolyzer & system engineering

We study electrolyzer and electrode system for the electrochemical reaction. This covers flow cell and membrane-electrode assembly (MEA) cell. Especially, we are interested in how to induce efficient catalytic reaction at three phase boundary at gas diffusion electrode (GDE) and seperate chemical products.

Real time spectroscopy is essential for the electrochemical CO2RR for mechanism study. We study operando X-ray absorption spectroscopy (XAS), which includes X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), to track oxidation states and coordinative structures of active materials. Furthermore, in-situ  Raman spectroscopies provides real time information of reaction intermediates bindings during electrochemical reaction which provides insight to understand reaction mechanism.