nano ∙ surface/interface ∙ charge/energy transfer ∙ light-matter interactions ∙ sustainable
These are keywords of our group who investigates catalytic science and technologies to improve the living conditions and the quality of the environment. Overall, we design and synthesize nanomaterials using rational and controllable methods, followed by characterizing their structures and a variety of (e.g., physical/chemical/electrical/optical) properties. Tuned properties of materials are utilized to selectively promote desirable reactions for mitigating gaseous emissions or producing clean fuels at low temperature. We gain mechanistic and kinetic insights into charge/energy transfer processes and reactions occurring at the solid-liquid or solid-gas interface using kinetic measurements, steady-state/transient spectroscopy, theoretical/computational analyses. From the findings, we acquire new design principles or feedback for iterative process optimization. Further research details are classified into four categories as per subject, which are described below.
Synthesis of Nanomaterials
Nanostructured materials are of great scientific interest and leading advances in science and technology as they have a high specific surface area and unique properties. For example, semiconductor nanoparticles show size-dependent properties (called quantum confinement), metal nanoparticles exhibit localized surface plasmon resonances (LSPRs), and magnetic materials possess superparamagnetism. We are enthusiastic about nanostructuring and defect engineering of metal, metal oxide, and quantum dots to understand and control their properties.
Surface/Interface Chemistry & Engineering
Heterogeneous catalysis is influenced by the number of available active sites, the strength of molecular adsorption to a catalyst surface (e.g., Sabatier principle), and the transfer of charge or energy between a catalyst and adsorbate, resulting in different catalytic activity and selectivity. Thus, it is critical to control surface/interface structures of catalysts and find a descriptor(s) that determines the rate at which the overall reaction proceeds. We investigate how the surface/interface structures of catalysts affect their catalytic behaviors through theoretical models and how we can leverage this understanding to guide rational design of catalysts.
Light-Matter Interactions at the Nanoscale
Catalysts provide active surface sites for a range of small molecules and often exhibit light excitation characteristics that confine charges and generate quantum effects. For example, gold colloids appear red to black depending on the particle size due to their LSPRs. The LSPR excitation generates energetic carriers that trigger or facilitate surface chemical reactions at reduced temperature, pressure, or bias along with enhanced stability of catalysts. This approach is particularly attractive due to the abundance of solar energy. Likewise, we have many interests in photoelectric effect, photonic crystals, biomimetic charge transfer, and photon upconversion to effectively harvest charge carriers.
Renewable Fuels Production & Environmental Remediation
According to the International Energy Agency (IEA)'s 2019 estimate, ca. 80% of the total world energy in 2017 was supplied by fossil fuels. However, fossil-fuel-based energy production/combustion systems emit carbon dioxide (CO2), sulfur oxides (SOx), nitrogen oxides (NOx), volatile organic compounds (VOCs), and some aerosols, such as particulate matters (PMs) and smog. High levels of the emissions are at the center of adverse environmental changes and serious health issues. In this respect, we investigate and develop catalytic materials and processes to mitigate (in)organic contaminants in air/water and environmentally produce emission-free fuels using abundant resources like H2O, CO2, and N2 for sustainable future.