catalyst – Lightsources.org

Green hydrogen: Nanostructured nickel silicide shines as a catalyst

2022/08/112022/08/24

Electrical energy from wind or sun can be stored as chemical energy in hydrogen, an excellent fuel and energy carrier. The prerequisite for this, however, is efficient electrolysis of water with inexpensive catalysts. For the oxygen evolution reaction at the anode, nanostructured nickel silicide now promises a significant increase in efficiency. This was demonstrated by a group from the HZB, Technical University of Berlin and the Freie Universität Berlin as part of the CatLab research platform with measurements among others at BESSY II.

Electrolysis might be a familiar concept from chemistry lessons in school: Two electrodes are immersed in water and put under voltage. This voltage causes water molecules to break down into their components, and gas bubbles rise at the electrodes: Oxygen gas forms at the anode, while hydrogen bubbles form at the cathode. Electrolysis could produce hydrogen in a CO₂-neutral way – as long as the required electricity is generated by fossil free energy forms such as sun or wind.

The only problem is that these reactions are not very efficient and extremely slow. To speed up the reactions, catalysts are used, based on precious and rare metals such as platinum, ruthenium or iridium. For large-scale use, however, such catalysts must consist of widely available and very cheap elements.

Read more on the HZB website

Image: Crystalline nickel silicide (left) is chemically transformed into nanostructured material with excellent catalytic properties for the electrolytic splitting of water and the production of valuable nitrile compounds.

Credit: © P. Menezes /HZB/TU Berlin

I am doing science that is more important than my sleep!

2022/01/122022/01/12

NSLS-II #LightSourceSelfie

Dan Olds is an associate physicist at Brookhaven National Laboratory where he works as a beamline scientist at NSLS-II. Dan’s research involves combining artificial intelligence and machine learning to perform real-time analysis on streaming data while beamline experiments are being performed. Often these new AI driven methods are critical to success during in situ studies of materials. These include next generational battery components, accident safe nuclear fuels, catalytic materials and other emerging technologies that will help us develop clean energy solutions to fight climate change.

Dan’s #LightSourceSelfie delves into what attracted him to this area of research, the inspiration he gets from helping users on the beamline and the addictive excitement that comes from doing science at 3am.

Promising new extra-large pore zeolite

2021/12/272022/01/01

An international research team, led in Spain by CSIC scientist Miguel A. Camblor, has discovered a stable aluminosilicate zeolite with a three dimensional system of interconnected extra-large pores, named ZEO-1.

Zeolites are crystalline porous materials with important industrial applications, including uses in catalytic processes. The pore apertures limit the access of molecules into and out of the inner confined space of zeolites, where reactions occur.

The research, published in Science, proved that ZEO-1 possesses these “extra-large” pores of around 10 Å (1 angstrom equals one ten billionth of a meter), but also smaller pores of around 7 Å, which is actually the size of traditional “large” pores.

Because of its porosity, strong acidity and high stability, ZEO-1 may find applications as a catalyst in fine chemistry for the production of pharmaceutical intermediates, in controlled substance release, for pollution abatement or as a support for the encapsulation of photo- or electroactive species (they react to light or an electric field).

“The crossings of its cages delimit super boxes, open spaces that can be considered nanoreactors to carry out chemical reactions in their confined space”, explains Miguel A. Camblor, researcher at the Instituto de Ciencia de Materiales de Madrid – CSIC.

To prove that this new zeolite may be useful in applications involving bigger molecules, researchers measured the adsorption to the inner surface of the zeolite of the dye Nile red – a big molecule. Moreover, they tested its performance in fluid catalytic cracking of heavy oil, a process the world still relies on to produce fuels. In both processes, the new zeolite performed better than the conventional large pore zeolite used nowadays.

This research is the result of an international collaboration between eight research centers in China, the USA, Sweden and Spain. The team was led by Fei-Jian Chen (Bengbu Medical College, China), Xiaobo Chen (China University of Petroleum), Jian Li (Stockholm University) and Miguel A. Camblor (Instituto de Ciencia de Materiales de Madrid, CSIC).

Structure determination with synchrotron light

The zeolite was discovered following a high-throughput screening methodology. The structure solution was challenging because the zeolite has a very complex structure, with a small crystal size (<200nm) but an exceedingly large cell volume.

“The combination of electron diffraction data with synchrotron powder X-ray diffraction data collected at the MSPD beamline of the ALBA Synchrotron and the Argonne National Laboratory (USA) made possible the accurate structure determination of ZEO-1″, says Camblor.

Read more on the ALBA website

Image: A perspective view of the extra-large pore of ZEO-1 along (100)

Green hydrogen: Why do certain catalysts improve in operation?

2021/08/092021/08/16

Crystalline cobalt arsenide is a catalyst that generates oxygen during electrolytic water splitting in the production of hydrogen. The material is considered to be a model system for an important group of catalysts whose performance increases under certain conditions in the course of electrolysis. Now a HZB-team headed by Marcel Risch has observed at BESSY II how two simultaneous mechanisms are responsible for this. The catalytic activity of the individual catalysis centres decreases in the course of electrolysis, but at the same time the morphology of the catalyst layer also changes. Under favourable conditions, considerably more catalysis centres come into contact with the electrolyte as a result, so that the overall performance of the catalyst increases.

As a rule, most catalyst materials deteriorate during repeated catalytic cycles – they age. But there are also compounds that increase their performance over the course of catalysis. One example is the mineral erythrite, a mineral compound comprising cobalt and arsenic oxides with a molecular formula of (Co₃(AsO₄)²∙8H₂O). The mineral stands out because of its purple colour. Erythrite lends itself to accelerating oxygen generation at the anode during electrolytic splitting of water into hydrogen and oxygen.

Read more in the HZB website

Image: Schematic of the electrochemical restructuring of erythrite. The fine needle-like structure melts during the conversion from a crystalline material to an amorphous one, which is porous like a Swiss cheese.

Credit: © HZB

In situ spectroscopy as a probe of electrocatalyst performance

2021/07/122021/07/28

Hydrogen fuel cells generally require expensive and scarce platinum catalysts in order to function. Researchers have created highly reactive platinum-nickel nanowires with the potential to reduce the amount of platinum required in fuel cells. Research at PIPOXS examines the atomic-level mechanisms of this catalyst, forming a foundation for the development and commercialization of more efficient fuel cell technology.

What is the new discovery?

The oxygen reduction reaction (ORR) is an important and often limiting component of hydrogen fuel cell operation. To facilitate this reaction, platinum-based catalysts are often used to increase its rate, though the expense and limited availability of Pt present challenges to its widespread use. In this work, researchers selectively replaced a portion of the nickel atoms of nickel nanowires with platinum to create platinum-nickel nanowires (PtNi-NWs) as high surface area catalysts that reduced the total amount of platinum required. These PtNi-NWs were found to be highly active, and so operando x-ray absorption spectroscopy and extended x-ray absorption fine structure (EXAFS) experiments were conducted at the PIPOXS beamline to assess the electronic and geometric changes occurring in these catalysts during their use. These data enabled the researchers to determine that the Pt formed an alloy with the Ni in the NW and that its interaction with oxygen remained constant regardless of the external potential applied.

Read more on the CHESS website

Image: Schematic showing the electrochemical cell used for the operando measurements, and how the EXAFS data can be used to deduce the chemistry happening during this reaction.

Helping to neutralise greenhouse gases

2020/07/082020/07/09

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

2020/03/232020/04/14

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, Na_0.67CoO₂, 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 Na_0.67CoO₂ is 2.30 Å, compared to 2.64 Å for CaCoO₃. The researchers then compared the OER performance of Na_0.67CoO₂ with IrO₂, Co₃O₄, and Co(OH)₂. They found that Na_0.67CoO₂ 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 Na_0.67CoO₂ also showed excellent stability under typical operating conditions.

Image: (extract, full image here) A new electrocatalyst prepared for this study, Na_0.67CoO₂, 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

2020/01/282020/02/10

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.

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

2019/10/162019/10/17

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

2019/10/092019/10/10

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 Co_1.5Mn_1.5O₄/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

2019/09/302019/10/03

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).

Image: Andy Beale works at Diamond Light Source.

New research possibilities at NanoMAX

2019/09/062019/09/12

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

2019/08/062019/09/19

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.

A step closer to smart catalysts for fuel generation

2019/07/222019/09/20

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

2019/06/242019/06/27

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 MgS₈and MgS₄at a fast reaction rate, reduction of MgS₄to Mg₃S₈, and a sluggish further reduction of Mg₃S₈to MgS. The in situ XAS analysis revealed that Mg₃S₈and 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

2019/06/192019/06/19

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 https://www.sciencedirect.com/science/article/pii/S0926337319305545

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)