Honors & Awards
NSF Graduate Research Fellow, National Science Foundation (2020-2023)
Education & Certifications
M.S., Stanford University, Chemical Engineering (2022)
B.S., University of California, Berkeley, Chemical Engineering (2020)
- Electrolyte type affects electrochemical bubble formation. Nature chemistry 2023
- Acid anion electrolyte effects on platinum for oxygen and hydrogen electrocatalysis COMMUNICATIONS CHEMISTRY 2022; 5 (1)
Self-Limiting Shell Formation in Cu@Ag Core-Shell Nanocrystals during Galvanic Replacement
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
2020; 11 (13): 5318–23
The understanding of synthetic pathways of bimetallic nanocrystals remains limited due to the complex energy landscapes and dynamics involved. In this work, we investigate the formation of self-limiting Cu@Ag core-shell nanoparticles starting from Cu nanocrystals followed by galvanic replacement with Ag ions. Bulk quantification with atomic emission spectroscopy and spatially resolved elemental mapping with electron microscopy reveal distinct nucleation regimes that produce nanoparticles with a tunable Ag shell thickness, but only up to a certain limiting thickness. We develop a quantitative transport model that explains this observed self-limiting structure as arising from the balance between entropy-driven interdiffusion and a positive mixing enthalpy. The proposed model depends only on the intrinsic physical properties of the system such as diffusivity and mixing energy and directly yields a high level of agreement with the elemental mapping profiles without requiring additional fit parameters.
View details for DOI 10.1021/acs.jpclett.0c01551
View details for Web of Science ID 000547468400057
View details for PubMedID 32530633
- Tracking the Dynamics of a Ag-MnO x Oxygen Reduction Catalyst Using In Situ and Operando X-ray Absorption Near-Edge Spectroscopy ACS ENERGY LETTERS 2023
- Hydrogen production with seawater-resilient bipolar membrane electrolyzers JOULE 2023; 7 (4): 765-781
Understanding the Stability of Manganese Chromium Antimonate Electrocatalysts through Multimodal In Situ and Operando Measurements.
Journal of the American Chemical Society
Improving electrocatalyst stability is critical for the development of electrocatalytic devices. Herein, we utilize an on-line electrochemical flow cell coupled with an inductively coupled plasma-mass spectrometer (ICP-MS) to characterize the impact of composition and reactant gas on the multielement dissolution of Mn(-Cr)-Sb-O electrocatalysts. Compared to Mn2O3 and Cr2O3 oxides, the antimonate framework stabilizes Mn at OER potentials and Cr at both ORR and OER potentials. Furthermore, dissolution of Mn and Cr from Mn(-Cr) -Sb-O is driven by the ORR reaction rate, with minimal dissolution under N2. We observe preferential dissolution of Cr totaling 13% over 10 min at 0.3, 0.6, and 0.9 V vs RHE, with only 1.5% loss of Mn, indicating an enrichment of Mn at the surface of the particles. Despite this asymmetric dissolution, operando X-ray absorption spectroscopy (XAS) showed no measurable changes in the Mn K-edge at comparable potentials. This could suggest that modification to the Mn oxidation state and/or phase in the surface layer is too small or that the layer is too thin to be measured with the bulk XAS measurement. Lastly, on-line ICP-MS was used to assess the effects of applied potential, scan rate, and current on Mn-Cr-Sb-O during cyclic voltammetry and accelerated stress tests. With this deeper understanding of the interplay between oxygen reduction and dissolution, testing procedures were identified to maximize both activity and stability. This work highlights the use of multimodal in situ characterization techniques in tandem to build a more complete model of stability and develop protocols for optimizing catalyst performance.
View details for DOI 10.1021/jacs.2c08600
View details for PubMedID 36453840
- A Versatile Li0.5FePO4 Reference Electrode for Nonaqueous Electrochemical Conversion Technologies ACS ENERGY LETTERS 2022: 230-235
- Origins of wear-induced tungsten corrosion defects in semiconductor manufacturing during tungsten chemical mechanical polishing APPLIED SURFACE SCIENCE 2022; 598
Facet-selective etching trajectories of individual semiconductor nanocrystals
2022; 8 (32): eabq1700
The size and shape of semiconductor nanocrystals govern their optical and electronic properties. Liquid cell transmission electron microscopy (LCTEM) is an emerging tool that can directly visualize nanoscale chemical transformations and therefore inform the precise synthesis of nanostructures with desired functions. However, it remains difficult to controllably investigate the reactions of semiconductor nanocrystals with LCTEM, because of the highly reactive environment formed by radiolysis of liquid. Here, we harness the radiolysis processes and report the single-particle etching trajectories of prototypical semiconductor nanomaterials with well-defined crystalline facets. Lead selenide nanocubes represent an isotropic structure that retains the cubic shape during etching via a layer-by-layer mechanism. The anisotropic arrow-shaped cadmium selenide nanorods have polar facets terminated by either cadmium or selenium atoms, and the transformation trajectory is driven by etching the selenium-terminated facets. LCTEM trajectories reveal how nanoscale shape transformations of semiconductors are governed by the reactivity of specific facets in liquid environments.
View details for DOI 10.1126/sciadv.abq1700
View details for Web of Science ID 000841491100034
View details for PubMedID 35947667
Engineering gold-platinum core-shell nanoparticles by self-limitation in solution
2022; 5 (1): 71
Core-shell particles with thin noble metal shells represent an attractive material class with potential for various applications ranging from catalysis to biomedical and pharmaceutical applications to optical crystals. The synthesis of well-defined core-shell architectures remains, however, highly challenging. Here, we demonstrate that atomically-thin and homogeneous platinum shells can be grown via a colloidal synthesis method on a variety of gold nanostructures ranging from spherical nanoparticles to nanorods and nanocubes. The synthesis is based on the exchange of low binding citrate ligands on gold, the reduction of platinum and the subsequent kinetically hindered growth by carbon monoxide as strong binding ligand. The prerequisites for homogeneous growth are low core-binding ligands with moderate fast ligand exchange in solution, a mild reducing agent to mitigate homonucleation and a strong affinity of a second ligand system that can bind to the shell's surface. The simplicity of the described synthetic route can potentially be adapted to various other material libraries to obtain atomically smooth core-shell systems.
View details for DOI 10.1038/s42004-022-00680-w
View details for Web of Science ID 000806740600001
View details for PubMedID 36697905
View details for PubMedCentralID PMC9814372
- Methods-A Practical Approach to the Reversible Hydrogen Electrode Scale JOURNAL OF THE ELECTROCHEMICAL SOCIETY 2022; 169 (6)
- Engineering metal-metal oxide surfaces for high-performance oxygen reduction on Ag-Mn electrocatalysts ENERGY & ENVIRONMENTAL SCIENCE 2022
- Rational solvent molecule tuning for high-performance lithium metal battery electrolytes NATURE ENERGY 2022
- Probing the Effects of Acid Electrolyte Anions on Electrocatalyst Activity and Selectivity for the Oxygen Reduction Reaction CHEMELECTROCHEM 2021; 8 (13): 2467-2478
Precise Colloidal Plasmonic Photocatalysts Constructed by Multistep Photodepositions
2020; 20 (12): 8661–67
Natural photosynthesis relies on a sophisticated charge transfer pathway among multiple components with precise spatial, energetic, and temporal organizations in the aqueous environment. It continues to inspire and challenge the design and fabrication of artificial multicomponent colloidal nanostructures for solar-to-fuel conversion. Herein, we introduce a plasmonic photocatalyst synthesized with colloidal methods with five integrated components including cocatalysts installed in orthogonal locations. The precise deposition of individual inorganic components on an Au/TiO2 nanodumbell nanostructure is enabled by photoreduction and photo-oxidation, which selectively occurs at the TiO2 tip sites and Au lateral sites, respectively. Under visible-light irradiation, the photocatalyst exhibited activity of oxygen evolution from water without scavengers. We demonstrate that each component is essential for improving the photocatalytic performance. In addition, mechanistic studies suggest that the photocatalytic reaction requires combining the hot charge carriers derived from exciting both the d-sp interband transition and the localized surface plasmon resonance of Au.
View details for DOI 10.1021/acs.nanolett.0c03431
View details for Web of Science ID 000599507100036
View details for PubMedID 33226246
- Factors and Dynamics of Cu Nanocrystal Reconstruction under CO2 Reduction ACS APPLIED ENERGY MATERIALS 2019; 2 (11): 7744–49
Low-dimensional perovskite nanoplatelet synthesis using in situ photophysical monitoring to establish controlled growth
2019; 11 (37): 17262–69
Perovskite nanoparticles have attracted the attention of research groups around the world for their impressive photophysical properties, facile synthesis and versatile surface chemistry. Here, we report a synthetic route that takes advantage of a suite of soluble precursors to generate CsPbBr3 perovskite nanoplatelets with fine control over size, thickness and optical properties. We demonstrate near unit cell precision, creating well characterized materials with sharp, narrow emission lines at 430, 460 and 490 nm corresponding to nanoplatelets that are 2, 4, and 6 unit cells thick, respectively. Nanoplatelets were characterized with optical spectroscopy, atomic force microscopy, scanning electron microscopy and transmission electron microscopy to explicitly correlate growth conditions, thickness and resulting photophysical properties. Detailed in situ photoluminescence spectroscopic studies were carried out to understand and optimize particle growth by correlating light emission with nanoplatelet growth across a range of synthetic conditions. It was found that nanoplatelet thickness and emission wavelength increase as the ratio of oleic acid to oleyl amine or the reaction temperature is increased. Using this information, we control the lateral size, width and corresponding emission wavelength of the desired nanoplatelets by modulating the temperature and ratios of the ligand.
View details for DOI 10.1039/c9nr04010b
View details for Web of Science ID 000487944000040
View details for PubMedID 31246216