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Chemists ID Catalytic 'Key' for Converting CO2 to Methanol

Results from experiments and computational modeling studies that definitively identify the "active site" of a catalyst commonly used for making methanol from CO2 will guide the design of improved catalysts for transforming this pollutant to useful chemicals.

Cryo-Electron Microscopy Achieves Unprecedented Resolution Using New Computational Methods

Cryo-electron microscopy (cryo-EM)--which enables the visualization of viruses, proteins, and other biological structures at the molecular level--is a critical tool used to advance biochemical knowledge. Now Berkeley Lab researchers have extended cryo-EM's impact further by developing a new computational algorithm instrumental in constructing a 3-D atomic-scale model of bacteriophage P22 for the first time.

New Study Maps Space Dust in 3-D

A new Berkeley Lab-led study provides detailed 3-D views of space dust in the Milky Way, which could help us understand the properties of this dust and how it affects views of distant objects.

Single-Angle Ptychography Allows 3D Imaging of Stressed Materials

Scientists have used a new X-ray diffraction technique called Bragg single-angle ptychography to get a clear picture of how planes of atoms shift and squeeze under stress.

New Feedback System Could Allow Greater Control Over Fusion Plasma

A physicist has created a new system that will let scientists control the energy and rotation of plasma in real time in a doughnut-shaped machine known as a tokamak.

Towards Super-Efficient, Ultra-Thin Silicon Solar Cells

Researchers from Ames Laboratory used supercomputers at NERSC to evaluate a novel approach for creating more energy-efficient ultra-thin crystalline silicon solar cells by optimizing nanophotonic light trapping.

Study IDs Link Between Sugar Signaling and Regulation of Oil Production in Plants

UPTON, NY--Even plants have to live on an energy budget. While they're known for converting solar energy into chemical energy in the form of sugars, plants have sophisticated biochemical mechanisms for regulating how they spend that energy. Making oils costs a lot. By exploring the details of this delicate energy balance, a group of scientists from the U.

High-Energy Electrons Probe Ultrafast Atomic Motion

A new technique synchronized high-energy electrons with an ultrafast laser pulse to probe how vibrational states of atoms change in time.

Rare Earth Recycling

A new energy-efficient separation of rare earth elements could provide a new domestic source of critical materials.

Two-Dimensional MXene Materials Get Their Close-Up

Researchers have long sought electrically conductive materials for economical energy-storage devices. Two-dimensional (2D) ceramics called MXenes are contenders.


Three SLAC Employees Awarded Lab's Highest Honor

At a March 7 ceremony, three employees of the Department of Energy's SLAC National Accelerator Laboratory were awarded the lab's highest honor ­- the SLAC Director's Award.

Dan Sinars Represents Sandia in First Energy Leadership Class

Dan Sinars, a senior manager in Sandia National Laboratories' pulsed power center, which built and operates the Z facility, is the sole representative from a nuclear weapons lab in a new Department of Energy leadership program that recently visited Sandia.

ORNL, HTS International Corporation to Collaborate on Manufacturing Research

HTS International Corporation and the Department of Energy's Oak Ridge National Laboratory have signed an agreement to explore potential collaborations in advanced manufacturing research.

Jefferson Lab Director Honored with Energy Secretary Award

Hugh Montgomery, director of the Department of Energy's Thomas Jefferson National Accelerator Facility (Jefferson Lab), was awarded The Secretary's Distinguished Service Award by the Secretary of Energy earlier this year.

New Projects to Make Geothermal Energy More Economically Attractive

Geothermal energy, a clean, renewable source of energy produced by the heat of the earth, provides about 6 percent of California's total power. That number could be much higher if associated costs were lower. Now scientists at the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) have launched two California Energy Commission-funded projects aimed at making geothermal energy more cost-effective to deploy and operate.

Southern Research Project Advances Novel CO2 Utilization Strategy

The U.S. Department of Energy's Office of Fossil Energy has awarded Southern Research nearly $800,000 for a project that targets a more cost-efficient and environmentally friendly method of producing some of the most important chemicals used in manufacturing.

Harker School Wins 2017 SLAC Regional Science Bowl Competition

After losing its first match of the day to the defending champions, The Harker School's team won 10 consecutive rounds to claim victory in the annual SLAC Regional DOE Science Bowl on Saturday, Feb. 11.

Francis Alexander Named Deputy Director of Brookhaven Lab's Computational Science Initiative

Alexander brings extensive management and leadership experience in computational science research to the position.

Kalinin, Paranthaman Elected Materials Research Society Fellows

Two researchers at Oak Ridge National Laboratory, Sergei Kalinin and Mariappan Parans Paranthaman, have been elected fellows of the Materials Research Society.

Two PNNL Researchers Elected to Membership in the National Academy of Engineering

Two scientists at the Pacific Northwest National Laboratory will become members of the prestigious National Academy of Engineering.


High-Energy Electrons Probe Ultrafast Atomic Motion

A new technique synchronized high-energy electrons with an ultrafast laser pulse to probe how vibrational states of atoms change in time.

Rare Earth Recycling

A new energy-efficient separation of rare earth elements could provide a new domestic source of critical materials.

Modeling the "Flicker" of Gluons in Subatomic Smashups

A new model identifies a high degree of fluctuations in the glue-like particles that bind quarks within protons as essential to explaining proton structure.

Rare Nickel Atom Has "Doubly Magic" Structure

Supercomputing calculations confirm that rare nickel-78 has unusual structure, offering insights into supernovas.

Microbial Activity in the Subsurface Contributes to Greenhouse Gas Fluxes

Natural carbon dioxide production from deep subsurface soils contributes significantly to emissions, even in a semiarid floodplain.

Stretching a Metal Into an Insulator

Straining a thin film controllably allows tuning of the materials' magnetic, electronic, and catalytic properties, essential for new energy and electronic devices.

How Moisture Affects the Way Soil Microbes Breathe

Study models soil-pore features that hold or release carbon dioxide.

ARM Data Is for the Birds

Scientists use LIDAR and radar data to study bird migration patterns, thanks to the Atmospheric Radiation Measurement (ARM) Climate Research Facility.

The Future of Coastal Flooding

Better storm surge prediction capabilities could help reduce the impacts of extreme weather events, such as hurricanes.

Estimating Global Energy Use for Water-Related Processes

Scientists find that water-related energy consumption is increasing across the globe, with pronounced differences across regions and sectors.


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Great Neck South High School Wins Regional Science Bowl at Brookhaven Lab

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Internship Program Helps Foster Development of Future Nuclear Scientists

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More Than 12,000 Explore Jefferson Lab During April 30 Open House

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Texas Tech Energy Commerce Students, Community Light up Tent City

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Scientists Boost Catalytic Activity for Key Chemical Reaction in Fuel Cells

Article ID: 666620

Released: 2016-12-16 09:05:58

Source Newsroom: Brookhaven National Laboratory

  • Credit: Brookhaven National Laboratory

    Dong Su in the control room of the aberration-corrected scanning transmission electron microscope (Hitachi HD2700C) at the Center for Functional Nanomaterials, a U.S. Department of Energy Office of Science User Facility at Brookhaven Lab. On the computer screens are images of the platinum-based nanoplates that Su and his collaborators developed. The nanoplates have a thick, ordered shell of platinum that surrounds a platinum and lead alloyed core. This special structure is thought to be behind the high catalytic activity and stability of the nanoplates.

  • Credit: Brookhaven National Laboratory

    Schematic diagram of the oxygen reduction reaction (reduction of O2 into H2O) on the Pt(110) surface of the PtPb/Pt nanoplates, with purple representing Pt atoms and orange representing Pb atoms.

UPTON, NY—Fuel cells are a promising technology for clean and efficient electrical power generation, but their cost, activity, and durability are key challenges to commercialization. Today's fuel cells use expensive platinum (Pt)-based nanoparticles as catalysts to accelerate the reactions involved in converting the chemical energy from renewable fuels—such as hydrogen, methanol, and ethanol—into electrical energy. Catalysts that incorporate less expensive metals inside the nanoparticles can help reduce cost and improve activity and durability, but further improvements to these catalysts are required before these fuel cells can be used in vehicles, generators, and other applications.

Now, scientists from the U.S. Department of Energy's (DOE) Brookhaven National Laboratory, California State University–Northridge, Soochow University, Peking University, and Shanghai Institute of Applied Physics have developed catalysts that can undergo 50,000 voltage cycles with a negligible decay in their catalytic activity and no apparent changes in their structure or elemental composition. As described in a paper published in the December 16 issue of Science, the catalysts are "nanoplates" that contain an atomically ordered Pt and lead (Pb) core surrounded by a thick uniform shell of four Pt layers.

To date, the most successful catalysts for boosting the activity of the oxygen reduction reaction (ORR)—a very slow reaction that significantly limits fuel cell efficiency—have been of the Pt-based core-shell structure. However, these catalysts typically have a thin and incomplete shell (owing to their difficult synthesis), which over time allows the acid from the fuel cell environment to leach into the core and react with the other metals inside, resulting in poor long-term stability and a short catalyst lifetime.

"The goal is to make the ORR as fast as possible with catalysts that have the least amount of platinum and the most stable operation over time," said corresponding author Dong Su, a scientist at Brookhaven Lab's Center for Functional Nanomaterials (CFN), a DOE Office of Science User Facility, who led the electron microscopy work to characterize the nanoplates. "Our PtPb/Pt catalysts show high ORR activity and stability—two parameters that are key to enabling a hydrogen economy—placing them among the most efficient and stable bimetallic catalysts reported for ORR."

Lattice strain for enhanced catalytic performance

In previous studies, scientists have shown that ORR activity can be optimally enhanced in core-shell catalysts by compressing the Pt atoms on one specific lattice surface plane called Pt(111). This compressive strain is induced by adding metals smaller in size than Pt, such as nickel, to the shell's core, and has the effect of weakening the binding of oxygen to the Pt surface, where the catalytic reaction takes place.

"The ideal ORR catalyst needs to help break bonds (between oxygen molecules) and form bonds (between oxygen and hydrogen), so oxygen can't be too strongly or too weakly bound to the platinum surface," explained Su. "Scientists have focused their research on the compressively strained Pt(111) surfaces, in which Pt atoms are squeezed across the surface, because the oxygen binding energy is optimized. In general, scientists thought that tensile strain on the same surface plane would result in overly strong binding of oxygen and thus hinder the ORR reaction."

But Su and his collaborators showed that introducing a large tensile strain along one direction of a different surface plane, Pt(110), could also improve ORR catalytic activity. They added Pb (which is larger than Pt) to the core of the Pt shell, causing the Pt atoms to stretch across the surface.

Nanoplate characterization and durability testing

After the research group led by Xiaoqing Huang, corresponding author from Soochow University, synthesized the nanoplates, Su characterized their structure and elemental composition at the CFN. Using electron diffraction patterns and images from high-resolution scanning transmission electron microscopy (STEM), both of which reveal the relative positions of atoms, he confirmed the core-shell structure and the composition and sequence of the atoms. To verify that the core contained Pt and Pb and that the shell contained Pt, he measured the change in energy of the electrons after they interacted with the nanoplates—a technique called electron energy-loss spectroscopy.

With this information, the team distinguished how the nanoplates formed with the individual Pt and Pb atoms. To their surprise, the surface planes were not Pt(111) but Pt(110), and these Pt(110) planes were under biaxial strain—compressive strain in one direction and tensile strain in the other—originating from the PtPb core.

In durability tests simulating fuel cell voltage cycling, Su's collaborators found that after 50,000 cycles there was almost no change in the amount of generated electrical current. In other words, the nanoplates had minimal decay in catalytic activity. After this many cycles, most catalysts exhibit some activity loss, with some losing more than half of their original activity.

Microscopy and synchrotron characterization techniques revealed that the structure and elemental composition of the nanoplates did not change following durability testing. "The electron microscopy work at CFN was critical in explaining why our nanoplates showed such high catalytic activity and stability," said Huang.

Compared to commercial Pt-on-carbon (Pt/C) catalysts, the team's PtPb/Pt nanoplates have one of the highest ORR activities to date, taking the amount of Pt used into account, and excellent durability. The team's nanoplates also showed high electrocatalytic activity and stability in oxidation reactions of methanol and ethanol.

"We believe the relatively thick and complete Pt layers play an important role in protecting the core," said Su.

To understand how the high ORR activity originates in the nanoplates, the scientists calculated the binding energy between oxygen atoms and Pt atoms on the surface. Their calculations confirmed the tensile strain on the Pt(110) surface was responsible for the enhanced ORR activity.

"This work opens up a new way to introduce large tensile strain on the stable Pt(110) plane to achieve very high activity for oxygen reduction catalysis. We believe that our approach will inspire efforts to design new nanostructured catalysts with large tensile strain for more efficient catalysis," said corresponding author Shaojun Guo of Peking University.

Eventually, the laboratory-level electrocatalysts will need to be tested in a larger fuel cell system, where real-world variables—such as pollutants that could impact surface reactivity—can be introduced.

In addition to the electron microscopy work performed at CFN, supported by DOE's Office of Science, this work involved theoretical calculations by Gang Lu's group at California State University–Northridge and synchrotron characterization by Jing-Yuan Ma at Shanghai Synchrotron Radiation Facility. This work was further supported by the National Basic Research Program of China, the National Natural Science Foundation of China, the Ministry of Science and Technology of the People's Republic of China, Soochow University, Peking University, the Young Thousand Talents Program, the Priority Academic Program Development of Jiangsu Higher Education Institutions, and the U.S. Army Research Office.

Brookhaven National Laboratory is supported by the Office of Science of the U.S. Department of Energy. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

Hydrogen fuel cell operation

A hydrogen fuel cell works similarly to a battery: it has two electrodes—a negatively charged anode and a positively charged cathode—where the chemical reactions occur, and an acid electrolyte that carries the resulting charged particles from one electrode to the other. Hydrogen enters the fuel cell at the anode, which is coated with a platinum catalyst. When the hydrogen molecules come into contact with the platinum, they split into hydrogen ions and free electrons in a reaction called hydrogen oxidation. The hydrogen ions travel through the electrolyte to the cathode; the electrons travel through an external circuit to generate electricity before arriving at the cathode. In the oxygen reduction reaction (ORR), oxygen molecules combine with the electrons that have completed their circuit and the hydrogen ions to produce water.

The rate of ORR is very slow because molecular oxygen has a very strong double bond that requires significant energy to be broken. As a result, the fuel cell suffers from a reduction in voltage (overpotential) that limits its efficiency.