• Phase Engineering of Nanomaterials for Sustainability

Metal nanomaterials usually crystallize in a thermodynamically stable crystal phase. Recently, fabricating metal nanocatalysts with unusual crystal phases has emerged as a hot topic given its versatility in creating nanocrystals with unconventional atom packing and exposed surfaces, opening a new avenue for improving catalytic properties. In this research direction, we aim to develop novel nanocatalysts based on phase engineering in an effort to tailor their catalytic performance, together with fundamental insights into the structure-property relationship. Particularly, when plasmonic metals are involved, the unique arrangement of atoms is expected to alter both the catalyst-adsorbate interaction and light-matter interaction, offering unprecedented opportunities for catalytic performance optimization.

• Single-Molecule Imaging of Heterogeneous Catalysis

Advancing molecular-level understanding of (support-)catalyst-adsorbate interaction is crucial to rationalize reaction mechanisms and to facilitate the design of optimal nanocatalysts. As depicted by the Sabatier principle, reagents adsorption on a catalyst should be neither too strong nor too weak in order to achieve an optimal catalytic performance. Although computational and analytical methods have been extensively employed to probe molecular adsorption on nanocatalysts, they are either carried out in vacuum or lack spatiotemporal resolution. The above challenge can be effectively addressed by employing single-molecule fluorescence imaging, which can resolve, at superb spatial and temporal resolutions, molecular adsorption under operando conditions. However, conventional studies have centered on entities or processes that emit fluorescence or are fluorescently labeled whereas most catalytic reactions do not involve fluorescent species. Recently, I developed a new imaging technique that can interrogate non- or weakly fluorescent processes at nanometer resolution, namely adCOMPEITS (adsorption-based competition-enabled imaging technique with super-resolution, manuscripts in preparation). By spatiotemporally quantifying the change in fluorescent signals, the spatial adsorption affinity map of non-fluorescent molecules on a single nanocatalyst can be obtained. In this research direction, we will employ the newly developed adCOMPEITS imaging technique to examine the (support-)catalyst-adsorbate interactions under operando conditions, aiming to revolutionize the mechanistic understanding of heterogeneous catalysis.

• Operando Imaging Technique Development

A typical catalytic reaction involves reagent adsorption on a catalyst surface followed by conversion into products. To unambiguously understand the reaction mechanisms, it is crucial to examine synchronously and quantitatively the adsorption behavior and conversion pathway of reagent molecules at single-molecule and single-particle levels. Although single-molecule fluorescence imaging can quantify molecular adsorption strength on single nanocatalysts, it is still challenging to access molecular structural information. This dilemma sets a huge barrier to explicitly understanding various catalytic processes, especially to identifying the catalytic species involving structural evolution to form products. In this research direction, we aim to develop new imaging techniques and/or platforms capable of in situ visualizing both the adsorption behavior and structural evolution of non-fluorescent species involved in catalytic reactions.