Helping to neutralise greenhouse gases

Researchers used the Canadian Light Source (CLS) at the University of Saskatchewan to create an affordable and efficient electrocatalyst that can transform CO2 into valuable chemicals. The result could help businesses as well as the environment.

Electrocatalysts help to collect CO2 pollution and efficiently convert it into more valuable carbon monoxide gas, which is an important product used in industrial applications. Carbon monoxide gas could also help the environment by allowing renewable fuels and chemicals to be manufactured more readily.

The end goal would be to try to neutralize the greenhouse gases that worsen climate change.

Precious metals are often used in electrocatalysts, but a team of scientists from Canada and China set out to find a less expensive alternative that would not compromise performance. In a new paper, the stability and energy efficiency of the team’s novel electrocatalyst offered promising results.

Read more on the Canadian Light Source website

Image : Schematic of an electrochemistry CO2-to-CO reduction reaction.

How a new electrocatalyst enables ultrafast reactions

The work provides rational guidance for the development of better electrocatalysts for applications such as hydrogen-fuel production and long-range batteries for electric vehicles.

The oxygen evolution reaction (OER) is the electrochemical mechanism at the heart of many processes relevant to energy storage and conversion, including the splitting of water to generate hydrogen fuel and the operation of proposed long-range batteries for electric vehicles. Because the OER rate is a limiting factor in such processes, highly active OER electrocatalysts with long-term stability are being sought to increase reaction rates, reduce energy losses, and improve cycling stability. Catalysts incorporating rare and expensive materials such as iridium and ruthenium exhibit good performance, but an easily prepared, efficient, and durable OER catalyst based on earth-abundant elements is still needed for large-scale applications.

Key insight: shorter O-O bonds
In an earlier study, a group led by John Goodenough (2019 Nobel laureate in chemistry) measured the OER activities of two compounds with similar structures: CaCoO3 and SrCoO3. They found that the CaCoO3 exhibited higher OER activity, which they attributed to its shorter oxygen–oxygen (O-O) bonds. Inspired by this, members of the Goodenough group have now analyzed a metallic layered oxide, Na0.67CoO2, which has an even more compact structure than CaCoO3. X-ray diffraction (XRD) experiments performed at the Advanced Photon Source (APS) confirmed that the shortest O-O separation in Na0.67CoO2 is 2.30 Å, compared to 2.64 Å for CaCoO3. The researchers then compared the OER performance of Na0.67CoO2 with IrO2, Co3O4, and Co(OH)2. They found that Na0.67CoO2 exhibited the highest current density, the lowest overpotential (a measure of thermodynamic energy loss), and the most favorable Tafel slope (sensitivity of the electric current to applied potential). The Na0.67CoO2 also showed excellent stability under typical operating conditions.

>Read more on the Advanced Light Source website

Image: (extract, full image here) A new electrocatalyst prepared for this study, Na0.67CoO2, consists of two-dimensional CoO2 layers separated by Na layers (not shown). The Co ions (blue spheres) have four different positions (Co1-Co4), and the distorted Co–O octahedra have varying oxygen–oxygen (O-O) separations (thick red lines connecting red spheres). All of the O-O bonds are shorter than 2.64 Å (the length of the corresponding bonds in a comparable material), and the shortest bonds are less than 2.40 Å. It turns out that O-O separation has a strong effect on the oxygen evolution reaction (OER) in this material.

New catalyst resists destructive carbon buildup in electrodes

Key challenges in the transition to sustainable energy include the long-duration storage of cheap, renewable electricity and the electrification of the heavy-freight transportation sector. Both challenges can be met using electrochemical cells. Solid oxide electrolysis cells are capable of highly efficient splitting of steam and CO2 to produce a synthetic H2–CO gas mixture (syngas), which can be converted into synthetic hydrocarbon transportation fuels using conventional industrial reactors. However, the efficiency of the process is limited by the risk of destructive carbon deposition inside the cells’ porous solid electrodes. A nickel catalyst is responsible for the carbon growth, but replacing this long-standing conventional catalyst has turned out to be highly challenging.

Now, researchers have used ambient-pressure x-ray photoelectron spectroscopy (APXPS) at ALS Beamlines 9.3.2 and 11.0.2 to probe the mechanisms by which carbon grows on different catalysts during CO2 electrolysis. Gadolinium-doped cerium oxide (GDC) is known to resist carbon growth, and the ambient-pressure experiments probed the degree and mechanism of this carbon resistance. The experimental data, subsequently confirmed by density functional theory calculations, revealed that the carbon atoms are energetically trapped by various oxygen species on the surface of GDC—a capability entirely lacking for nickel.

>Read more on the Advanced Light Source website

Image: Artistic representation of a nickel-based electrode as a broken down fuel pump and of a cerium-based electrode as a new, productive pump. Credit: Cube3D

NSLS-II scientist named DOE Office of Science Distinguished Fellow

Scientists from the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory have garnered two out of five “Distinguished Scientists Fellow” awards announced today by the DOE’s Office of Science.

Theoretical physicist Sally Dawson, a world-leader in calculations aimed at describing the properties of the Higgs boson, and José Rodriguez, a renowned chemist exploring and developing catalysts for energy-related reactions, will each receive $1 million in funding over three years to pursue new research objectives within their respective fields. (…)

José Rodriguez (NSLS-II)

For discoveries of the atomic basis of surface catalysis for the synthesis of sustainable fuels, and for significantly advancing in-situ methods of investigation using synchrotron light sources.”

Rodriguez will devote his funding to the development and construction of new tools for performing extremely rapid, time-resolved measurements to track the reaction mechanisms of catalytic processes as they occur under variable conditions—like those encountered during real-world reactions important to energy applications. These include processes on metal-oxide catalysts frequently used in the production of clean fuels and other “green” chemicals through hydrogenation of carbon monoxide and carbon dioxide, or the conversion of methane to hydrogen.

“At a microscopic level, the structure of a catalyst and the chemical environment around the active sites—where chemical bonds are broken and reformed as reactants transform into new products—change as a function of time, thus determining the reaction mechanism,” said Rodriguez. “We can learn a lot about the nature of the active sites under steady-state conditions, with no variations in temperature, pressure, and reaction rate. But to really understand the details of the reaction mechanism, we need ways to track what happens under transient or variable conditions. This funding will allow us to build new instrumentation that works with existing capabilities so we can study catalysts under variable conditions—and use what we learn to improve their performance.”

>Read more on the NSLS-II website

Synergistic Co−Mn oxide catalyst for oxygen reduction reactions

Researchers employed synchrotron-based X-ray absorption spectroscopy (XAS) at CHESS to investigate the synergistic interaction of bimetallic Co1.5Mn1.5O4/C catalysts… under real-time operando electrochemical conditions.

Identifying the catalytically active site(s) in the oxygen reduction reaction (ORR) is critical to the development of fuel cells and other technologies. Researchers employed synchrotron-based X-ray absorption spectroscopy (XAS) at CHESS to investigate the synergistic interaction of bimetallic Co1.5Mn1.5O4/C catalysts – which exhibit impressive ORR activity in alkaline fuel cells – under real-time operando electrochemical conditions. Under steady state conditions, both Mn and Co valences decreased at lower potentials, indicating the conversion from Mn-(III,IV) and Co(III) to Mn(II,III) and Co(II), respectively. Changes in the Co and Mn valence states are simultaneous and exhibited periodic patterns that tracked the cyclic potential sweeps.

>Read more on the CHESS website

Image: Schematic of the in situ XAS electrochemical cell. Working electrode (WE, catalyst on carbon paper) and counter electrode (CE, carbon rod) were immersed in 1 M KOH solution. The reference electrode was connected to the cell by a salt bridge to minimize IR drops caused by the resistance in the thin electrolyte layer within the X-ray window.

Worldwide scientific collaboration develops catalysis breakthrough

A new article  just published in Nature Catalysis shows the simple ways of controlling the structure of platinum nanoparticles and tuning their catalytic properties. 

Research led by Cardiff Catalysis Institute (CCI) in collaboration with scientists from Lehigh University, Jazan University, Zhejiang University, Glasgow University, University of Bologna, Research Complex at Harwell (RCaH), and University College London have combined their unique skills to develop and understand using advanced characterisation methods (particularly TEM and B18 at Diamond Light Source), how it is possible to use a simple preparation method to control and manipulate the structures of metal nanoparticles. These metal nanoparticles are widely used by industry as innovative catalysts for the production of bulk chemicals like polymers, liquid fuels (e.g., diesel, petrol) and other speciality chemicals (pharmaceutical products).

>Read more on the Diamond Light Source website

Image: Andy Beale works at Diamond Light Source.

New research possibilities at NanoMAX

X-rays can penetrate materials and are therefore useful for studying chemical processes as they occur inside reactors, cells, and batteries. A common ingredient in such chemical systems is metal nanoparticles, which are often used as catalysts for important reactions. As the NanoMAX beamline provides a very small X-ray focal spot, single nanoparticles can in principle be studied as they perform their catalytic functions.

In this paper, we show that gold nanoparticles sitting inside an electrochemical cell can be imaged at NanoMAX. These preliminary results come from nanoparticles around 60 nm (60 millionths of a millimetre) in size, and we show that even smaller particles could be studied. If successful, future experiments will allow “filming” nanoparticles as they catalyze reactions in real-time, and give new understanding of how catalysis works. That could in turn help design new materials for energy conversion, chemical production, and water purification.

>Read more on the MAX IV Laboratory
Image (extract, full image here): Coherent Bragg imaging of 60 nm Au nanoparticles under electrochemical control at the NanoMAX beamline

Using reed waste for sustainable batteries

With the changing climate, researchers are focusing on finding sustainable alternatives to conventional fuel cells and battery designs. Traditional catalysts used in vehicles contribute to increasing carbon dioxide emissions and mining for materials used in their design has a negative impact on the environment. Prof. Shuhui Sun, a researcher from the Institut National de la Recherche Scientifique (INRS) in Montreal, and his team used the Canadian Light Source (CLS) at the University of Saskatchewan to investigate an Iron-Nitrogen-Carbon catalyst using reed waste.

They hope to use the bio-based materials to create high-performance fuel cells and metal-air batteries, which could be used in electric cars. “An efficient oxygen electrocatalyst is extremely important for the development of high-performance electrochemical energy conversion and storage devices. Currently, the rare and expensive Pt-based catalysts are commonly used in these devices. Therefore, developing highly efficient and low-cost non-precious metal (e.g., Fe-based) catalysts to facilitate a sluggish cathodic oxygen reduction reaction (ORR) is a key issue for metal air batteries and fuel cells,” said Qilang Wei, the first author of the paper.

>Read more on the Canadian Light Source website

A step closer to smart catalysts for fuel generation

Researchers at the Universidade Federal do Rio Grande do Sul in Brazil in collaboration with the ALBA Synchrotron have performed the first detailed measurement of the strong metal-support interaction (SMSI) effect in Cu-Ni nanoparticles supported on cerium oxide.

A better understanding of this effect is essential for developing smart catalysts that are more selective, stable and sustainable. The quest for the best catalysts in industry has been a long one, but a new study by Universidade Federal do Rio Grande do Sul in Brazil, in collaboration with the ALBA Synchrotron, has come a step closer. For the first time, researchers have found evidence of what could be the origin of the SMSI effect in catalysts supported on cerium oxide.

Catalysts are used to increase the reaction rate of a given chemical reaction, and have applications in a wide variety of fields. In heterogeneous catalysis, the catalyst is usually composed of metal nanoparticles supported on metal oxides. Among them, CeO2-based catalysts have unique structural and atomic properties that make them suitable in the cutting-edge environmental industry of fuel cells and hydrogen. In this field, they are being explored as high-end photocatalytic reactors for the thermal splitting of water and carbon dioxide. However, what has been termed as the SMSI effect can undermine their desired properties.

>Read more on the ALBA website

Image: (extract, full picture here) Near Ambient Pressure – X-ray Photoemission Spectroscopy allowed the identification of the chemical components of the nanoparticles in situ.

Catalyst improves cycling life of magnesium/sulfur batteries

Comprising earth-abundant elements, cathodes made of magnesium/sulfur compounds could represent the next step in battery technology. However, despite being dendrite free and having a high theoretical energy density compared with lithium batteries, magnesium/sulfur batteries have suffered from high polarization and extremely limited recharging capabilities. To gain electrochemical insights into magnesium/sulfur batteries during charge–discharge cycles, researchers used the Advanced Light Source (ALS) to investigate and optimize battery chemistry.

The in situ x-ray absorption spectroscopy (XAS) capabilities at ALS Beamlines 5.3.1 and 10.3.2 provided information on the oxidation state of sulfur under real operating conditions. The group found that the conversion of sulfur in the first discharging process was divided into three stages: formation of MgSand MgSat a fast reaction rate, reduction of MgSto Mg3S8, and a sluggish further reduction of Mg3Sto MgS. The in situ XAS analysis revealed that Mg3Sand MgS are more electrochemically inert and cannot revert to the active forms of sulfur, thereby dramatically reducing the battery’s cycling life.

>Read more on the ALS website

Image: Efforts to develop magnesium/sulfur batteries have been stymied by a loss of capacity after the first discharging process. In situ XAS revealed the accumulation of Mg3S8 and MgS during the discharging process, which are inert forms of the magnesium/sulfur compounds. Introducing a titanium-sulfide catalyst activated the compounds, reversing the chemical mechanism so that the battery could be recharged multiple times.


Publication of the first scientific paper

June 1, 2019 marks a historically important accomplishment for SESAME, where the very first scientific paper presenting results using data obtained at SESAME’s X-ray absorption fine structure/X-ray fluorescence (XAFS/XRF) spectroscopy beamline was published in Applied Catalysis B: Environmental.

S: Bac et al. Applied Catalysis B: Environmental, 259, 2019, 117808

Synchrotron measurements performed at SESAME were carried out by the research group of Associate Professor Emrah Ozensoy (Bilkent University Chemistry Department and UNAM-National Nanotechnology Center Ankara, Turkey), in collaboration with the research group of Professor Ahmet Kerim Avcı (Boğaziçi University, Chemical Engineering Department, Istanbul, Turkey) and Dr Messaoud Harfouche (XAFS/XRF beamline scientist, SESAME, Allan, Jordan).
The paper entitled Exceptionally active and stable catalysts for CO2 reforming of glycerol to syngas is the outcome of a measurement campaign at SESAME in July 2018 and focuses on the catalytic valorization of a biomass waste material (i.e. glycerol) to obtain synthesis gas (or syngas, CO + H2). Glycerol is an important renewable feedstock for the large-scale catalytic production of synthetic liquid fuels through a process called Fischer-Tropsch synthesis. In the words of Emrah Ozensoy “XAFS/XRF experiments performed at SESAME were instrumental for us to understand the electronic structure of the Co/CoOx and Ni/NiOx nanoparticles serving as the catalytic active sites. Particularly, complementing the experimental data acquired in our labs with the results obtained at SESAME allowed us to examine the nature of the fresh catalysts and compare them with that of the spent catalysts obtained after the catalytic reaction, revealing crucial molecular-level insights regarding the catalytic aging and poisoning mechanisms.”

>Read more on the SESAME website

Image: Kerem Emre Ercan Some of the researchers who contributed to the publication and data acquisition (from left to right, Yusuf Koçak, Kerem E. Ercan, and M. Fatih Genişel)

New materials for the reduction of vehicle pollution

Research develops nanostructured material with high oxygen storage and release capacity for the improvement of catalytic converters

Complete combustion of both fossil and biofuels generates carbon dioxide (CO2) and water as final products. However, incomplete combustion of these substances can occur in automobile engines, generating important pollutants such as carbon monoxide (CO), hydrocarbons, and nitrogen oxides (such as NO and NO2).
To reduce the emission of these toxic substances, an equipment called a catalytic converter is used in the exhaust of vehicles. Materials called catalysts promote and accelerate chemical reactions without being consumed during the process. They retain on their surface the reactant molecules, weakening the bonds between the atoms and causing the pollutants to be converted into less harmful gases.
The action of the catalytic converter happens in three stages. The first stage converts the nitrogen oxides into nitrogen (N2) and oxygen (O2) gases. The second stage breaks down bonds of unburnt hydrocarbons and carbon monoxide, turning them into CO2. Finally, the third stage has an oxygen sensor to regulate the intake of air and fuel to the engine, so that the amount of oxygen is always close to the most efficient for the different reactions.

>Read more on the Brazilian Light Laboratory (LNLS) website

Catalyst renders nerve agents harmless

Scientists used a multimodal approach to understand how a catalyst decomposes nerve agents in real-life environments

A team of scientists including researchers at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory has studied a catalyst that decomposes nerve agents, eliminating their harmful and lethal effects. The research was published Friday, April 19, in the Journal of Physical Chemistry Letters.

“Our work is part of an ongoing, multiagency effort to protect soldiers and civilians from chemical warfare agents (CWAs),” said Anatoly Frenkel, a physicist with a joint appointment at Brookhaven Lab and Stony Brook University and the lead author on the paper. “The research requires us to understand molecular interactions on a very small scale, and to develop special characterization methods that are capable of observing those interactions. It is a very complex set of problems that also has a very immediate societal impact.”

>Read more on the National Synchrotron Light Source-II website

Image: Lead author Anatoly Frenkel is shown at NSLS-II’s X-ray Powder Diffraction beamline, where part of the research was conducted.

Urea susbstitutes noble metal catalysts

… for the photodegradation of organic polluants.

A new laser-based technique developed by the Institute of Materials Science (ICMAB-CSIC) uses urea, a common substance in the chemical industry and a low-cost alternative to noble metal co-catalyst, to enable a more efficient, one-step production of hybrid graphene-based organic-inorganic composite layers for environmental remediation, photodegradation of antibiotic contaminants from wastewater. The composition and chemical bonds of the urea-enriched thin layers were studied in detail using synchrotron light at the ALBA Synchrotron.
Human activity is increasing the amount of pollutants in water and air, as well as in all sorts of materials at home and work place. The existence of antibiotic contamination is undeniably one of the most threatening challenges to date, at a time when antibiotic-resistant bacteria has already been flagged as the next world-wide pandemic crisis.
Semiconductor photocatalysts have long been investigated for environmental remediation because they can degrade or mineralize a wide range of organic contaminants as well as pathogens. Research focuses on addressing some drawbacks that prevent their use on a large scale. On the one hand, many photocatalysts are activated only by UV radiation which represents solely a small fraction of the total available solar emission. On the other hand, the recombination of the photogenerated  electron-hole pairs that enable the decomposition of the pollutant is usually faster than the oxidation reactions that cause the degradation of organic molecules. As a consequence, noble metal co-catalysts acting as electron scavengers, such as gold or platinum, are needed in the process.

Image: Researchers Ángel Pérez  del Pino and Enikö György from the ICMAB-CSIC together with Ibraheem Yousef, scientists responsible of MIRAS beamline at ALBA.

Watching molecules in a light-triggered catalyst ring ‘like an ensemble of bells’

A better understanding of these systems will aid in developing next-generation energy technologies.

Photocatalysts ­– materials that trigger chemical reactions when hit by light – are important in a number of natural and industrial processes, from producing hydrogen for fuel to enabling photosynthesis.
Now an international team has used an X-ray laser at the Department of Energy’s SLAC National Accelerator Laboratory to get an incredibly detailed look at what happens to the structure of a model photocatalyst when it absorbs light.
The researchers used extremely fast laser pulses to watch the structure change and see the molecules vibrating, ringing “like an ensemble of bells,” says lead author Kristoffer Haldrup, a senior scientist at Technical University of Denmark (DTU). This study paves the way for deeper investigation into these processes, which could help in the design of better catalysts for splitting water into hydrogen and oxygen for next-generation energy technologies.
“If we can understand such processes, then we can apply that understanding to developing molecular systems that do tricks like that with very high efficiency,” Haldrup says.

>Read more on the Linac Coherent Light Source at SLAC website

Image: When photocatalyst molecules absorb light, they start vibrating in a coordinated way, like an ensemble of bells. Capturing this response is a critical step towards understanding how to design molecules for the efficient transformation of light energy to high-value chemicals.
Credit: Gregory Stewart/SLAC National Accelerator Laboratory

Platinum forms nano-bubbles

Technologically important noble metal oxidises more readily than expected.

Platinum, a noble metal, is oxidised more quickly than expected under conditions that are technologically relevant. This has emerged from a study jointly conducted by the DESY NanoLab and the Vienna University of Technology. Devices that contain platinum, such as the catalytic converters used to reduce exhaust emissions in cars, can suffer a loss in efficacy as a result of this reaction. The team around principal author Thomas Keller, from DESY and the University of Hamburg, is presenting its findings in the journal Solid State Ionics. The result is also a topic at the users’ meeting of DESY’s X-ray light sources with more than 1000 participants currently taking place in Hamburg.
“Platinum is an extremely important material in technological terms,” says Keller. “The conditions under which platinum undergoes oxidation have not yet been fully established. Examining those conditions is important for a large number of applications.”
The scientists studied a thin layer of platinum which had been applied to an yttria-stabilised zirconia crystal (YSZ crystal), the same combination that is used in the lambda sensor of automotive exhaust emission systems. The YSZ crystal is a so-called ion conductor, meaning that it conducts electrically charged atoms (ions), in this case oxygen ions. The vapour-deposited layer of platinum serves as an electrode. The lambda sensor measures the oxygen content of the exhaust fumes in the car and converts this into an electrical signal which in turn controls the combustion process electronically to minimize toxic exhausts.

>Read more on the DESY (PETRA III) website

Image: Electron microscope view into the interior of a platinum bubble. The cross-section was exposed with a focused ion beam. Below the hollow Pt bubble the angular YSZ crystal can be seen.
Credit: DESY, Satishkumar Kulkarni