Abstract
The control of morphology in the synthesis of Rh nanocrystals can be used to precisely tailor the electronic surface structure; this in turn directly influences their performance in catalysis applications. Many works have brought attention to the development of Rh nanostructures with low-index surfaces, but limited effort has been devoted to the study of high-index and surface defect-enriched nanocrystals as they are not favored by thermodynamics because of the involvement of high-energy surfaces and increased surface-to-volume ratios. In this work, we demonstrate an aqueous synthesis of concave Rh nanotetrahedra (CTDs) serving as efficient catalysts for energy conversion reactions. CTDs are surface defect-rich structures that form through a slow growth rate and follow the four-step model of metallic nanoparticle growth. Via the tuning of the surfactant concentration, the morphology of Rh CTDs evolved into highly excavated nanotetrahedra (HETDs) and twinned nanoparticles (TWs). Unlike the CTD surfaces with abundant adatoms and vacancies, HETDs and TWs have more regular surfaces with layered terraces. Each nanocrystal type was evaluated for methanol electrooxidation and hydrogen evolution from hydrolysis of ammonia borane, and the CTDs significantly showed the best catalytic performance because of defect enrichment, which benefits the surface reactivity of adsorbates. In addition, both CTDs and HETDs have strong absorption near the visible light region (382 and 396 nm), for which they show plasmon-enhanced performance in photocatalytic hydrogen evolution under visible light illumination. CTDs are more photoactive than HETDs, likely because of more pronounced localized surface plasmon resonance hot spots. This facile aqueous synthesis of large-surface-area, defect-rich Rh nanotetrahedra is exciting for the fields of nanosynthesis and catalysis.
| Original language | English |
|---|---|
| Pages (from-to) | 4448-4458 |
| Number of pages | 11 |
| Journal | Chemistry of Materials |
| Volume | 30 |
| Issue number | 13 |
| DOIs | |
| State | Published - Jul 10 2018 |
Funding
The authors are grateful for the technical support from Ms. I-Hui Chen, the technician in the Advanced Nano/ Micro-Fabrication and Characterization laboratory of Academia Sinica (AS), for TEM characterization and operation training. A portion of the electron microscopy was performed as part of a user project through Oak Ridge National Laboratory’s Center for Nanophase Materials Sciences, which is a U.S. Department of Energy (DOE) Office of Science User Facility, and using instrumentation provided by the U.S. DOE Office of Nuclear Energy, Fuel Cycle R&D Program, and the Nuclear Science User Facilities. The authors especially thank Ms. Mei-Ying Chung, the technician in the Institute of Chemistry (IOC) of AS, for performing SEM and ICP-OES analyses. All catalytic reactions were performed with the instruments in the Center of Catalytic Facility in IOC, AS. This work is financially supported by the Ministry of Science and Technology, Taiwan (MOST 106-2113-M-001-030-MY2), Academia Sinica (Innovative Materials and Analytical Techniques), and Executive Yuan, Taiwan (Government Policy Allocation Plan for Key S&T Developments). A portion of the electron microscopy was performed as part of a user project through Oak Ridge National Laboratory's Center for Nanophase Materials Sciences, which is a U.S. Department of Energy (DOE) Office of Science User Facility, and using instrumentation provided by the U.S. DOE Office of Nuclear Energy, Fuel Cycle R&D Program and the Nuclear Science User Facilities. The authors especially thank Ms. Mei-Ying Chung, the technician in the Institute of Chemistry (IOC) of AS, for performing SEM and ICP-OES analyses.