Atomic Flaws Create Surprising, High-Efficiency UV LED Materials

Subtle surface defects increase UV light emission in greener, more cost-effective LED and catalyst materials

Light-emitting diodes (LEDs) traditionally demand atomic perfection to optimize efficiency. On the nanoscale, where structures span just billionths of a meter, defects should be avoided at all costs—until now.

A team of scientists from the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory and Stony Brook University has discovered that subtle imperfections can dramatically increase the efficiency and ultraviolet (UV) light output of certain LED materials.

“The results are surprising and completely counterintuitive,” said Brookhaven Lab scientist Mingzhao Liu, the senior author on the study. “These almost imperceptible flaws, which turned out to be missing oxygen in the surface of zinc oxide nanowires, actually enhance performance. This revelation may inspire new nanomaterial designs far beyond LEDs that would otherwise have been reflexively dismissed.”

>Read more on the NSLS-II website

Image: The research team, front to back and left to right: Danhua Yan, Mingzhao Liu, Klaus Attenkoffer, Jiajie Cen, Dario Stacciola, Wenrui Zhang, Jerzy Sadowski, Eli Stavitski.

 

Structure and Catalytic Activity of Copper Nanoparticles

Research investigates the addition of ceria on the activity of catalysts for the water-gas shift reaction

Catalysts are substances that promote and accelerate chemical reactions without being consumed during the process and are widely used in industrial processes to produce various chemicals.

Catalysts based on copper nanoparticles dispersed in an oxide support benefit various reactions, such as the synthesis of methanol, the alcohol dehydrogenation, or the water gas shift (WGS) reaction which is one of the main processes for hydrogen production on an industrial scale. In this reaction, carbon monoxide reacts with water to produce carbon dioxide CO2 and hydrogen gas H2.

>Read more on the LNLS website

Figure 1: Correlation between the bond length of CuO and the catalyst turnover frequency (TOF) for the catalysts analyzed under WGS conditions with different proportions of copper and ceria.

 

2017’s Top-10 Discoveries and Scientific Achievements

Each year we compile a list of the biggest advances made by scientists, engineers, and those who support their work at the U.S. Department of Energy’s Brookhaven National Laboratory. From unraveling new details of the particle soup that filled the early universe to designing improvements for batteries, x-ray imaging, and even glass, this year’s selections span a spectrum of size scales and fields of science. Read on for a recap of what our passion for discovery has uncovered this year.  (…)

4. Low-Temperature Hydrogen Catalyst

Brookhaven chemists conducted essential studies to decipher the details of a new low-temperature catalyst for producing high-purity hydrogen gas. Developed by collaborators at Peking University, the catalyst operates at low temperature and pressure, and could be particularly useful in fuel-cell-powered cars. The Brookhaven team analyzed the catalyst as it was operating under industrial conditions using x-ray diffraction at the National Synchrotron Light Source (NSLS). These operando experiments revealed how the configuration of atoms changed under different operating conditions, including at different temperatures. The team then used those structural details to develop models and a theoretical framework to explain why the catalyst works so well, using computational resources at Brookhaven’s Center for Functional Nanomaterials (CFN).

 >Read more on the NSLS-II website

 

New Catalyst Gives Artificial Photosynthesis a Big Boost

Inspired by plants: Inorganic catalyst converts electrical energy to chemical energy at 64% efficiency

Researchers have created a new catalyst that brings them one step closer to artificial photosynthesis — a system that would use renewable energy to convert carbon dioxide (CO2) into stored chemical energy.

As in plants, their system consists of two linked chemical reactions: one that splits water (H2O) into protons and oxygen gas, and another that converts CO2 into carbon monoxide (CO). The CO can then be converted into hydrocarbon fuels through an established industrial process. The system would allow both the capture of carbon emissions and the storage of energy from solar or wind power.

Yufeng Liang and David Prendergast – scientists at the Molecular Foundry, a nanoscale research facility at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) – performed theoretical modeling work used to interpret X-ray spectroscopy measurements made in the study, published Nov. 20 in Nature Chemistry. This work was done in support of a project originally proposed by the University of Toronto team to the Molecular Foundry, a DOE Office of Science User Facility.

 

>Read more on the ALS website

Image: Phil De Luna of University of Toronto is one of the lead authors of a new study that reports a low-cost, highly efficient catalyst for chemical conversion of water into oxygen. The catalyst is part of an artificial photosynthesis system in development at the University of Toronto.
Credit: Tyler Irving/University of Toronto

Making the world go round

A look into the structure of a prominent heterogeneous catalyst

Fluid catalytic cracking, a century old chemical conversion process utilizing porous composites of zeolite and clay, up to this day provides the majority of the world’s gasoline. Owing to harsh reaction environments and feedstock impurities the employed catalysts deactivate, necessitating their continuous fractional replacement with major refineries requiring up to 40 tons of fresh catalyst in total on a daily basis. Using a combination of ptychographic, x-ray diffraction and -fluorescence tomography researchers from PSI and ETH elucidated the structural changes behind catalyst deactivation.

Read more on the PSI website.

Image: Cropped – Ptychographic image reconstructions. a Volume reconstructions of FCC1, FCC2, and FCC3. Orthoslices through the retrieved electron density maps are shown in b–d, respectively. Presented are bottom up (z–x) and orthogonal views (y–z, y–x). Cutting planes are represented by dotted lines. Shown in e–g are enlarged versions of selected areas. Common to all subfigures is the linear grey scale for the electron density. Selected diffusion highways (-) are highlighted in pink, hydrocarbon deposits by a red triangle, and the ASA shell by a blue cross. Voxel size is about (20 nm)3. Scale bars are 5 µm