A5009050911- Advanced Photocatalysis Techniques
- Mesoporous Materials and Catalysis
- 2D Materials and Applications
- Ammonia Synthesis and Nitrogen Reduction
- X-ray Diffraction in Crystallography
- Electrocatalysts for Energy Conversion
- Crystallization and Solubility Studies
- MXene and MAX Phase Materials
- Inorganic Fluorides and Related Compounds
- Graphene research and applications
- Nanomaterials for catalytic reactions
- Copper-based nanomaterials and applications
- Catalytic Processes in Materials Science
- Advancements in Battery Materials
- Block Copolymer Self-Assembly
- Machine Learning in Materials Science
- Quantum Dots Synthesis And Properties
- TiO2 Photocatalysis and Solar Cells
- Gold and Silver Nanoparticles Synthesis and Applications
- Advanced Battery Materials and Technologies
- Molecular Junctions and Nanostructures
- Iron oxide chemistry and applications
- Conducting polymers and applications
- Supercapacitor Materials and Fabrication
- Advanced Memory and Neural Computing
University of North Carolina at Chapel Hill
2016-2025
Applied Physical Sciences (United States)
2015-2020
Communities In Schools of Orange County
2017
Northwestern University
2011-2014
École Polytechnique Fédérale de Lausanne
2010-2013
Cornell University
2006-2012
University of Cambridge
2009
ETH Zurich
2009
National Institute for Materials Science
2008
University of Pennsylvania
2008
We study hematite (α-Fe2O3) photoelectrodes for water splitting by examining the fate of photogenerated holes. Using H2O2 as an efficient hole scavenger, we collect all holes that arrive at electrode/electrolyte interface. This provides ability to distinguish between and quantify bulk surface recombination processes involved in photoelectrochemical oxidation water. Below 1.0 VRHE, electrolyte kinetics limits performance but above 1.2 VRHE becomes limiting factor.
The study of the optoelectronic effects plasmonic metal nanoparticles on semiconductors has led to compelling evidence for plasmon-enhanced water splitting. We review relevant physics, device geometries, and research progress in this area. focus localized surface plasmons their semiconductors, particularly terms energy transfer, scattering, hot electron transfer.
The synthesis of ordered mesoporous metal composites and metals is a challenge because have high surface energies that favor low areas. We present results from the self-assembly block copolymers with ligand-stabilized platinum nanoparticles, leading to lamellar CCM-Pt-4 inverse hexagonal (CCM-Pt-6) hybrid mesostructures nanoparticle loadings. Pyrolysis CCM-Pt-6 produces an platinum-carbon nanocomposite open large pores (>/=10 nanometers). Removal carbon leads porous mesostructures. has very...
Phosphorene, a two-dimensional (2D) monolayer of black phosphorus, has attracted considerable theoretical interest, although the experimental realization monolayer, bilayer, and few-layer flakes been significant challenge. Here, we systematically survey conditions for liquid exfoliation to achieve first large-scale production with demonstrated at 10 g scale. We describe rapid approach quantifying thickness 2D phosphorus show that produced by our are crystalline unoxidized, while air exposure...
An experimental study of the influence gold nanoparticles on α-Fe2O3 photoanodes for photoelectrochemical water splitting is described. A relative enhancement in efficiency at photon frequencies corresponding to plasmon resonance was observed. This observed only electrode geometries with metal particles that were localized semiconductor-electrolyte interface, consistent observation minority carrier transport electrolyte most significant impediment achieving high efficiencies this system.
Intermetallic compounds PtPb and PtBi have been prepared in nanoparticle form by dissolving Pt Pb or Bi precursors anhydrous methanol coreducing the metal with sodium borohydride. The average domain size determined from pXRD is 10 nm. particles characterized pXRD, SEM, STEM, EDX, CBED. SEM STEM images show to be aggregated, forming clusters chains. BET surface area of nanoparticles was measured using Kr as adsorbing gas. electrocatalytic oxidation formic acid as-prepared has studied rotating...
A Pt-based electrocatalyst for direct fuel cells, Pt3Ti, has been prepared in the form of nanoparticles. Pt(1,5-cyclooctadiene)Cl2 and Ti(tetrahydrofuran)2Cl4 are reduced by sodium naphthalide tetrahydrofuran to atomically disordered Pt3Ti nanoparticles (FCC-type structure: Fm3̅m; a = 0.39 nm; particle size 3 ± 0.4 nm). These transformed larger ordered (Cu3Au-type Pm3̅m; 0.3898 37 23 nm) annealing above 400 °C. Both show lower onset potentials oxidation formic acid methanol than either pure...
Phosphorene is emerging as an important two-dimensional semiconductor, but controlling the surface chemistry of phosphorene remains a significant challenge. Here, we show that controlled oxidation determines composition and spatial distribution resulting oxide. We used X-ray photoemission spectroscopy to measure binding energy shifts accompany oxidation. interpreted these spectra by calculating shift for 24 likely bonding configurations, including phosphorus oxides hydroxides located on...
Single crystals of a cyclodextrin-based metal-organic framework (MOF) infused with an ionic electrolyte and flanked by silver electrodes act as memristors. They can be electrically switched between low high conductivity states that persist even in the absence applied voltage. In this way, these small blocks nanoporous sugar function non-volatile RRAM memory elements repeatedly read, erased, re-written. These properties derive from current within MOF deposition nanometer-thin passivating...
The electronic structure of 2D semiconductors depends on their thickness, providing new opportunities to engineer for energy conversion, electronics, and catalysis. Here we show how a 3D semiconductor, black phosphorus, becomes active solar-to-chemical conversion when it is thinned material. increase in its band gap, from 0.3 eV (3D) 2.1 (2D monolayer), accompanied by 40-fold enhancement the formation chemical products. Despite this enhancement, smaller flakes also have shorter excited state...
Metal-organic frameworks (MOFs) are typically poor electrical conductors, which limits their uses in sensors, fuel cells, batteries, and other applications that require electrically conductive, high surface area materials. Although metal nanoclusters (NCs) often added to MOFs, the properties of these hybrid materials have not yet been explored. Here, we show adding NCs a MOF only imparts moderate conductivity an otherwise insulating material but also renders it photoconductive, with...
Because of their loosely bound electrons, electrides offer physical properties useful in chemical synthesis and electronics. For these applications others, nanosized advantages, but to-date no electride has been synthesized as a nanomaterial. We demonstrate experimentally that Ca2N, layered which layers atoms are separated by 2D electron gas (2DEG), can be exfoliated into two-dimensional (2D) nanosheets using liquid exfoliation. The flakes stable nitrogen atmosphere or select organic...
We report the generalized synthesis of metal nanoparticles with liquid-like behavior. introduce a thiol-containing ionic liquid, N,N-dioctyl-N-(3-mercaptopropyl)-N-methylammonium bromide, which serves as ligand for platinum, gold, palladium, and rhodium nanoparticles. A rapid reduction using THF-soluble salts in presence thiol generates tunable sizes size distributions. The as-synthesized are solid decompose before melting. Upon exchange halide anion an amphiphilic sulfonate anion, however,...
The morphology of TiO2 plays an important role in the operation solid-state dye-sensitized solar cells. By using polyisoprene-block-ethyleneoxide (PI-b-PEO) copolymers as structure directing agents for a sol-gel based synthesis mesoporous TiO2, we demonstrate strategy detailed control semiconductor on 10 nm length scale. careful adjustment polymer molecular weight and titania precursor content is used to systematically vary material its influence upon cell performance investigated....
We review layered and ultrathin electrides with exciting properties like high electrical mobility, carrier concentrations, low work functions.
The ability to alter distances between atoms is among the most important tools in materials design. Despite this importance, controlling interlayer distance stacks of 2D remains a challenge. Here we show from first-principles that stacking electrenes-a new class electron-donating materials-with other provides control. resulting donor-acceptor heterostructures have 1 Å less than van der Waals layered but more covalent or ionic bonds. This yields quasi-bonds exhibit characteristics both...
Despite the interest in MXenes past decade, are often highly disordered, which can complicate their study and use. For example, nearly all have a random mixture of surface terminations (−O, −OH, −F). In addition, restacked 3D films turbostratic disorder contain ions, solvent, other species between layers. Here, we report Y2CF2, layered crystal with unit cell isostructural to MXene, layers capped only by fluoride anions. We directly synthesize through high-temperature solid-state reaction,...
Electrides are exotic materials that typically have electrons present in well-defined lattice sites rather than within atoms. Although all known electrides an electropositive metal cation adjacent to the electride site, effect of electronegativity on properties is not yet known. Here, we examine trivalent carbides with varying degrees and experimentally synthesize Sc2C. Our studies identify material as a two-dimensional (2D) electride, even though Sc more electronegative any previously found...