Surface Science and Surface Functionalization
We apply atomic/molecular layer deposition (ALD/MLD) for surface functionalization. ALD/MLD is a vapor phase method to achieve a thin film growth by using a well-defined surface chemistry. Two (or more) complementary, quantitative surface reactions performed in an alternating manner result in the deposition of a solid in a layer-by-layer fashion (as shown in Figure 1). ALD/MLD offers outstanding conformality on high-aspect ratio structures, thickness control at the Angstrom level, and tunable film structure. MLD systems for polymer testimony can be consolidated with ALD strategies for inorganic material development to create organic/inorganic mixture materials. Highly porous metal oxide films with well-defined porous structures and controllable film thickness can be produced by oxidizing metalcone hybrid polymer films deposited by MLD.
Nanostructured Materials for Catalysis
Heterogeneous catalysts are widely used due to many advantages including the easiness of separating the catalysts by filtration and recoverability after reaction. Our studies focus on preparing nanostructured catalysts with high catalytic activity, high reaction selectivity, and high thermal stability by using ALD/MLD and traditional liquid-based methods. ALD has received increasing attention for the preparation of metal nanoparticles (NPs). Recently, we prepared Pt-Co bimetallic NPs by ALD and these catalysts showed excellent activity and selectivity for various hydrogenation reactions. We successfully prepared single atom catalysts by ALD on various substrates. We also prepared various nanostructured catalysts, such as metal NPs encapsulated with a porous film with well-defined porous structures and controllable film thickness and gaps between metal NPs and porous shells (Figure 2). These core-shell structured catalysts only sinter at much higher temperatures, and the porous shell can also increase the reaction selectivity through reactant molecular discrimination. We use these metal NPs, bimetallic NPs, single atom catalysts, single atom alloys, and nanostructured catalysts for various catalytic reactions.
Figure 2. Scheme of supported metal catalysts: (a) Pt NPs on porous γ-alumina particles, (b) self-assembled monolayers selectively deposited on the surface of Pt NPs, (c) aluminum alkoxide MLD film coated on the surfaces of Pt NPs and the catalyst support, and (d) porous films and gaps formed after removal of the organic components.
Nanostructured Materials for Energy Storage
ALD has the potential to become a critical tool in the area of energy conversion and storage including lithium-ion and sodium-ion batteries, solid oxide fuel cells, and supercapacitors. Our current focus, in this field, is on rechargeable lithium-ion batteries. Using the film thickness and conformality control of the ALD process, we aim not only to protect the electrode materials from undesired degradation due to charge-discharge cycling and thus improve the life span of the battery, but also to improve the initial capacity of the battery (as shown in Figure 3 for our recent results).
Nanostructured Materials for Environmental Remediation
Ecological contamination is a genuine issue in today’s quickly developing society. The measure of natural contaminations in wastewater streams and unstable natural mixtures in the environment has consistently expanded throughout the last few decades. New methodologies are obliged to address this issue. Photocatalytic corruption is one strategy to decrease and wipe out these contaminants. We have successfully been able to tune the photocatalytic nature of titania, a widely used photocatalyst, to meet the desired need for the application of environmental remediation.