- Press Release Distribution

How catalysts age

How catalysts age
( PSI researchers have developed a new tomography method with which they can measure chemical properties inside catalyst materials in 3-D extremely precisely and faster than before. The application is equally important for science and industry. The researchers published their results today in the journal Science Advances. The material group of vanadium phosphorus oxides (VPOs) is widely used as a catalyst in the chemical industry. VPOs have been used in the production of maleic anhydride since the 1970s. Maleic anhydride in turn is the starting material for the production of various plastics, increasingly including biodegradable ones. In industry, the catalytic materials are typically used for several years, because they play an important role in the chemical reactions but are not consumed in the process. Nevertheless, a VPO catalyst changes over time as a result of this use. In a collaborative effort, scientists from two research divisions at the Paul Scherrer Institute PSI - the Photon Science Division and the Energy and Environment Division - together with researchers at ETH Zurich and the Swiss company Clariant AG, have now investigated in detail the ageing process of VPO catalysts. In the course of their research, they also developed a new experimental method. Two methods... Clariant AG is one of the world's leading companies for specialty chemicals. Clariant provided PSI with two samples: first, a sample of previously unused VPO catalyst; and second, a sample of VPO catalyst that had been used in industrial operations for four years. It had long been known that VPOs change over years of use and exhibit a slight loss of the desired properties. Until now, however, it was not completely clear which processes in the nano-structure and at the atomic scale were responsible for the observed decrease in performance. The PSI researchers investigated this question with state-of-the-art material characterisation techniques. To make the chemical structure of the samples visible on the nanoscale, they combined two methods: The first was a specific tomography method previously developed at PSI called ptychographic X-ray computed tomography, which uses X-rays from the Swiss Light Source SLS and can non-destructively image the interior of the sample in 3-D and with nanometre resolution. To this, secondly, the researchers added a local transmission spectroscopy method that additionally revealed the chemical properties of the material in each volume element of the tomograms. "Basically, we collected four-dimensional data," explains Johannes Ihli, a researcher at PSI and one of the study authors: "We reconstructed a high-resolution 3-D representation of our sample in which the individual volume elements - called voxels - have an edge length of only 26 nanometres. In addition, we have a quantitative X-ray transmission spectrum for each of these voxels, the analysis of which tells us the local chemistry." These spectra allowed the scientists to determine for each voxel some of the most fundamental chemical quantities. These included the electron density, the vanadium concentration, and the degree of oxidation of the vanadium. Since the examined VPO catalysts are a so-called heterogeneous material, these quantities change at various scales throughout its volume. This in turn either defines or limits the material's functional performance. ... and a new algorithm The step-by-step procedure to obtain this data was to measure the sample for a 2-D projection image, then rotate it a tiny bit, measure again, and so on. This process was then repeated at various other energies. With the previous method, about fifty thousand individual 2-D images would have been necessary, and these would have been combined into about a hundred tomograms. For each of the two samples, this would have meant about one week of pure measuring time. "The experimental stations at SLS are in great demand and booked up all year round," explains Manuel Guizar-Sicairos, likewise a PSI researcher and the principal investigator of this study. "We therefore cannot afford to carry out measurements that take so long." Data collection had to become more efficient. Zirui Gao, lead author of the study, achieved this in the form of a new principle of data acquisition and an associated reconstruction algorithm. "For the 3-D reconstruction of tomograms, you need images from many angles," Gao explains. "But our new algorithm manages to extract the required amount of information even if you increase the distance between the angles about tenfold - that is, if you only take about one-tenth of the 2-D images." In this way, the researchers succeeded in obtaining the required data in only about two days of measurement, consequently saving a lot of time and thus also costs. Larger pores and missing atoms This is what the measurements of the two samples showed: As expected, the fresh VPO had many small pores that were evenly distributed in the material. These pores are important because they provide the surface on which catalysis can take place. In contrast, the structure of the VPO sample that had been in use for four years had changed on the nanoscale. There were larger and fewer cavities. The material in between them showed larger, elongated crystalline shapes. Changes were also found on the molecular level: Over time, voids, also called holes, had appeared in the atomic lattice. Their existence had previously only been suspected. With the acquired chemical information at the nanoscale, the researchers were now able to confirm this hypothesis and also to show exactly where the voids were located: at the site of specific vanadium atoms that were now missing. "The fact that the relative content of vanadium decreases over time was already known," says Gao. "But we were now able to show for the first time at which point in the crystal lattice these atoms are missing. Together with our other findings, this confirms the previous assumption that these holes in the atomic lattice can serve as additional active sites for the process of catalysis." This also implies that the increase in these imperfections is a welcome effect: They enhance the catalytic activity and thus at least partially counteract the loss of activity caused by the decreasing number of pores. "Our new, detailed results could help industrial companies optimise their catalysts and make them more durable," Gao says.


Text: Paul Scherrer Institute/Laura Hennemann

Images are available to download at

Additional information Nanoworlds in 3-D - article from 11 March 2020

Contact Zirui Gao
Research group for coherent X-ray scattering
Paul Scherrer Institute, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
Telephone: +41 56 310 2910, e-mail: [English, Chinese]

Dr. Manuel Guizar-Sicairos
Research group for coherent X-ray scattering
Paul Scherrer Institute, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
Telephone: +41 56 310 34 09, e-mail: [English, Spanish]

Dr. Johannes Ihli
Research group for coherent X-ray scattering
Paul Scherrer Institute, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
Telephone: +41 56 310 40 50, e-mail: [German, English]

Dr. Mirko Holler
Laboratory for Macromolecules and Bioimaging
Paul Scherrer Institute, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
Telephone: +41 56 310 36 13, e-mail: [German, English]

Original publication Sparse ab initio X-ray transmission spectro-tomography for nanoscopic compositional analysis of functional materials
Z. Gao, M. Odstrcil, S. Böcklein, D. Palagin, M. Holler, D. Ferreira Sanchez, F. Krumeich, A. Menzel, M. Stampanoni, G. Mestl, J.A. van Bokhoven, M. Guizar-Sicairos, J. Ihli
Science Advances 9 June 2021 (online)
DOI: 10.1126/sciadv.abf6971

[Attachments] See images for this press release:
How catalysts age


Researchers develop tool to aid in development, efficiency of hydrogen-powered cars

Researchers develop tool to aid in development, efficiency of hydrogen-powered cars
Widespread adoption of hydrogen-powered vehicles over traditional electric vehicles requires fuel cells that can convert hydrogen and oxygen safely into water - a serious implementation problem. Researchers at the University of Colorado Boulder are addressing one aspect of that roadblock by developing new computational tools and models needed to better understand and manage the conversion process. Hendrik Heinz, an associate professor in the Department of Chemical and Biological Engineering, is leading the effort in partnership with the University of California Los Angeles. His team recently published new findings on the subject in Science Advances. Fuel cell electric vehicles combine ...

Lower and safer doses of laughing gas relieve treatment-resistant depression in phase 2 trial

A single one-hour treatment with nitrous oxide - also known as laughing gas - can relieve symptoms of treatment-resistant depression for several weeks, according to a phase 2 clinical trial involving 28 participants. By showing that a 25% concentration of the gas still has therapeutic effects, the results suggest that lower concentrations of nitrous oxide could be useful against depression in the clinic while bringing a lower risk of side effects. Inhaled nitrous oxide is commonly used as a sedative agent in dental and medical offices, but the gas has also attracted attention as a possible treatment for depression. A previous study showed that nitrous oxide had marked ...

Curtin study finds aspirin takes the headache out of restoration

New Curtin research has shown how a readily available, cheap and safe-to-use product found in the medicine cabinet of most homes could be the key to better ecological restoration practices with major benefits for the environment and agriculture. The study revealed that aspirin, which naturally occurs in the bark of the willow tree and other plants, can improve the survival of grass species important for ecological restoration and sustainable pasture when applied in a seed coating. Lead researcher Dr Simone Pedrini from the ARC Centre for Mine Site Restoration in Curtin's School of Molecular and Life Sciences, said salicylic acid has been used for its medicinal properties for more than 4000 years and its modern synthetic version, acetylsalicylic acid, or aspirin, is one ...

Rapamycin changes the way our DNA is stored

Rapamycin changes the way our DNA is stored
Our genetic material is stored in our cells in a specific way to make the meter-long DNA molecule fit into the tiny cell nucleus of each body cell. An international team of researchers at the Max Planck Institute for Biology of Ageing, the CECAD Cluster of Excellence in Ageing research at the University of Cologne, the University College London and the University of Michigan have now been able to show that rapamycin, a well-known anti-ageing candidate, targets gut cells specifically to alter the way of DNA storage inside these cells, and thereby promotes gut health and longevity. This effect has been observed in flies and mice. The researchers believe this finding will open up new possibilities for targeted therapeutic interventions ...

New study underscores the role of race and poverty in COVID-19

BOSTON - A new analysis by researchers at Massachusetts General Hospital (MGH) offers a novel perspective on the disproportionate impact that COVID-19 has had on people of color, low-income populations, and other structurally disadvantaged groups. Their findings, published in a research letter to the END ...

Study shows new links between high fat diets and colon cancer

For decades, physicians and dieticians have urged people to limit their intake of high fat foods, citing links to poor health outcomes and some of the leading causes of death in the U.S., such as diabetes, heart disease and cancer. According to the Centers for Disease Control and Prevention, dietary components high in saturated fats such as red meat are thought to be risk factors for colon cancer. Diet is thought to strongly influence the risk of colorectal cancer, and changes in food habits might reduce up to 70% of this cancer burden. Other known epidemiological risk factors are family history, inflammatory bowel disease, ...

SARS-CoV-2 detectable -- though likely not transmissible -- on hospital surfaces

SARS-CoV-2 detectable -- though likely not transmissible -- on hospital surfaces
Watching what was happening around the world in early 2020, University of California San Diego School of Medicine researchers knew their region would likely soon be hit with a wave of patients with COVID-19, the infection caused by the coronavirus SARS-CoV-2. They wondered how the virus persists on surfaces, particularly in hospitals, and they knew they had only a small window of time to get started if they wanted to capture a snapshot of the "before" situation -- before patients with the infection were admitted. After a call late one Sunday night, a team assembled in the ...

Acoustical evolution increases battle between predator, prey

Acoustical evolution increases battle between predator, prey
MELVILLE, N.Y., June 9, 2021 -- In the evolutionary battle between hunter and hunted, sound plays an integral part in the success or failure of the hunt. In the case of bats vs. moths, the insects are using acoustics against their winged foes. During the 180th Meeting of the Acoustical Society of America, which will be held virtually June 8-10, Thomas Neil, from the University of Bristol, will discuss how moth wings have evolved in composition and structure to help them create anti-bat defenses. The session, "Moth wings are acoustic metamaterials," will take place Wednesday, June 9, at 1 p.m. Eastern U.S. Nocturnal moths ...

Pandemic quarantine acoustically contributes to mental, physical health degradation

MELVILLE, N.Y., June 9, 2021 -- The prolonged impact of the COVID-19 pandemic and the interaction restrictions created widespread lockdown fatigue and increased social tension in multiunit housing. But small improvements in quality-of-life routines may help people cope with the health restrictions better than they previously could. During the 180th Meeting of the Acoustical Society of America, which will be held virtually June 8-10, Braxton Boren, from American University, will discuss noise prevention techniques and the use of alterative acoustic stimulation to help those who find themselves in pandemic-related lockdowns. The session, "The Soundscape of Quarantine," will take place Wednesday, June 9, at 1:45 p.m. Eastern U.S. While there have been studies about ...

SARS-CoV-2 protease cuts human proteins; possible link to COVID-19 symptoms

The SARS-CoV-2 papain-like protease (PLpro) plays an essential role in processing viral proteins needed for replication. In addition, the enzyme can cut and inactivate some human proteins important for an immune response. Now, researchers reporting in ACS Infectious Diseases have found other targets of PLpro in the human proteome, including proteins involved in cardiovascular function, blood clotting and inflammation, suggesting a link between the inactivation of these proteins and COVID-19 symptoms. Viruses like SARS-CoV-2 make multiple proteins as one long "polyprotein." Viral enzymes called proteases recognize specific amino acid sequences in this polyprotein and cut them to release individual proteins. ...


Cat-borne parasite Toxoplasma induces fatally bold behavior in hyena cubs

Nature article: Dieting and its effect on the gut microbiome

NIH scientists describe "Multi-Kingdom Dialogue" between internal, external microbiota

Melatonin in mice: there's more to this hormone than sleep

Wild bees need deadwood in the forest

A triple-system neural model of maladaptive consumption

Milk protein could help boost blueberries' healthfulness

Seeking a treatment for IBS pain in tarantula venom

Addressing inequity in air quality

Roughness of retinal layers, a new Alzheimer's biomarker

Study links sleep apnea in children to increased risk of high blood pressure in teen years

Black patients with cirrhosis more likely to die, less likely to get liver transplant

Researchers outline specific patterns in reading in Russian

These sea anemones have a diverse diet. And they eat ants

Viruses as communication molecules

Spirituality can promote the health of breast cancer survivors

Tiny ancient bird from China shares skull features with Tyrannosaurus rex

University of Minnesota Medical School report details the effects of COVID-19 on adolescent sexual health

Odd smell: flies sniff ammonia in a way new to science

Fracture setting method could replace metal plates, with fewer complications

Sneeze cam reveals best fabric combos for cloth masks (video)

'Lady luck' - Does anthropomorphized luck drive risky financial behavior?

People willing to pay more for coffee that's ethical and eco-friendly, meta-analysis finds

Low-cost imaging technique shows how smartphone batteries could charge in minutes

Pleistocene sediment DNA from Denisova Cave

Quantum birds

Antibody therapy rescues mice from lethal nerve-muscle disease

Life in these star-systems could have spotted Earth

Cutaneous reactions after mRNA COVID-19 vaccines

Skin reactions after COVID-19 vaccination: Rare, uncommonly recur after second dose

[] How catalysts age