In situ infrared absorption spectroscopy systems including surface-enhanced infrared absorption spectroscopy (SEIRAS): We have developed several infrared absorption spectroscopy systems including SEIRAS to study the surface-adsorbed intermediates in the solid-liquid and solid-gas interfaces during the electrochemical and photochemical reactions. These reactions play crucial roles in controlling the performance of photocatalysts, electrocatalysts and secondary batteries. Our SEIRAS system exhibits higher S/N and a time resolution of “~second”, which enable the investigation of surface-adsorbed intermediates during the electrochemical reactions. Different materials (powder and thin film samples) can be measured in this system.

The reaction mechanism of catalytic CO2 reduction reaction: Understanding the role of the oxidation state of the Cu surface and surface-adsorbed intermediate species in electrochemical CO2 reduction is crucial for the development of selective CO2-to-fuel electrocatalysts. The electrochemical CO2 reduction mechanism over the Cu catalysts with various oxidation states was studied by using in situ surface-enhanced infrared absorption spectroscopy (SEIRAS), in situ soft X-ray absorption spectroscopy (Cu L-edge), and online gas chromatography measurements. The major theme of this work is that in situ SEIRAS results show the coexistence of CO atop and CO bridge as the reaction intermediates during CO2 reduction and that the selectivity of CO2-to-ethylene conversion is further enhanced in the CV-treated Cu electrode. The Cu catalysts modulated by the electrochemical method exhibit different oxidation states and reaction intermediates as well as electrocatalytic properties. (Reference: Journal of the American Chemical Society, 2020, 142 (6), 2857-2867.)

The reaction mechanism of advanced battery materials: Li-rich layered oxide cathodes with conventional transition metal cation and unique oxygen anion redox reactions deliver high capacities in Li-ion batteries. However, the oxygen redox process causes the oxygen release, voltage fading/hysteresis, and sluggish electrochemical kinetics, which undermine the performance of these materials. By combining operando quick-scanning X-ray absorption spectroscopy with online gas chromatography, the effect of the local electronic structure is elucidated on the reaction mechanism and electrochemical kinetics of Li-rich cathodes. The cation oxidation process of LLC cathode is kinetically slower than that of HLC cathode and the cation oxidation potential is shifted, likely due to the local coordination associated with different Li/O ratios. The obtained insights into the effect of local electronic structure on the reaction mechanism and kinetics provide a better understanding and control of Li-rich cathodes. (Reference: Advanced Functional Materials, 2022, 32, 2112394.) 

The development of advanced battery system: Lithium metal anodes form a dendritic structure after cycling which causes an internal short circuit in flammable electrolytes and results in battery fires. Today's separators are insufficient for suppressing the formation of lithium dendrites. Herein, we report on the use of mesoporous silica thin films (MSTFs) with perpendicular nanochannels (pore size ∼5 nm) stacking on an anodic aluminum oxide (AAO) membrane as the MSTF⊥AAO separator for advancing Li metal batteries. The nanoporous MSTF⊥AAO separator with novel inorganic structures shows ultra-long term stability of Li plating/stripping in Li–Li cells at an ultra-high current density and capacity (10 mA cm−2 and 5 mA h cm−2). The excellent performance of the MSTF⊥AAO separator is due to good wetting of electrolytes, straight nanopores with negative charges, uniform Li deposition and blocking the finest dendrite. (Reference: Journal of Materials Chemistry A 2020, 8, 5095-5104.)