Tag: carbon dioxide

A Close Look at a Copper-Titanium Catalyst Under CO2 Hydrogenation

A Close Look at a Copper-Titanium Catalyst Under CO2 Hydrogenation

A major facet of transitioning from fossil fuels to green and renewable energy solutions involves the removal, capture and storage of carbon dioxide (CO2) from the environment. One method is by CO2 hydrogenation, which requires a catalyst to spur the reaction, frequently including metal-oxide catalysts in which metal-support interactions (MSIs) play an important role. 

Researchers from the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory, Stony Brook University, DOE’s Argonne National Laboratory and several other institutions used a suite of in situ techniques to study the behavior and structural and chemical properties of a Cu@TiOx core@shell catalyst under CO2 hydrogenation. Their work was published in ACS Catalysis.

In a core@shell structure, one type of active system (the core) is encapsulated by a shell of a different material to enhance catalytic performance. These experiments focused on an inverse oxide/metal catalyst configuration using a copper nanowire core with a titanium oxide (titania) shell. Such catalysts have been shown to offer improved stability and activity over the conventional metal/oxide arrangement.

Through the use of an entire range of in situ characterization techniques – including time-resolved experiments with X-ray absorption spectroscopy (XAS), ambient pressure X-ray photoelectron spectroscopy (AP-XPS), environmental transmission electron microscopy (E-TEM), and X-ray diffraction at the 17-BM-B beamline of the Advanced Photon Source, a DOE Office of Science user facility at Argonne – the investigators sought to achieve a comprehensive understanding of the structure and behavior of the Cu@TiOx catalyst under CO2 activation and hydrogenation, a functional picture that cannot be obtained with typical steady state studies.

The dynamic characteristics of this catalyst system became immediately evident even during the standard pretreatment used for CO2 hydrogenation, when the H2 pretreatment at temperatures of above 250 degrees Celsius resulted in cracking of the titania shell and migration of Cu particles from the core to the top of the oxide shell. This, along with other configuration changes, was caused by metal-support interactions. The migrating Cu particles are about 20-40 nm in diameter and are speckled with clusters of TiOx and Cu-Ti-Ox. With this altered structure, the system displayed highly dynamic yet wholly reversible catalytic characteristics that were dependent on temperature and chemical environment.

Read more on Argonne website

Image: E-TEM that match with the XRD results.

Trapping and storing carbon dioxide underground

Trapping and storing carbon dioxide underground

A team led by the University of Oslo in Norway, in collaboration with the University of Maryland in USA, is investigating how to massively store carbon dioxide (CO2) underground by copying nature. Through a chemical reaction, carbon dioxide can be trapped naturally inside the Earth’s subsurface and stored as solid minerals, called carbonates. The researchers are now carrying out experiments at the ESRF with the aim to accelerate such a process.

Carbon dioxide levels in the atmosphere are higher than ever, mainly due to the burning of fossil fuels and other anthropogenic activities. This, in turn, increases global temperatures and impacts sea levels and the ocean ecosystems.

A potential solution to this crisis would be to trap and store CO2 underground as solid minerals, which is a natural process that occurs over long periods thanks to the reaction of CO2 with rocks in the Earth’s crust and mantle.

Scientists have been studying the injection of CO2 in the subsurface for years. For example, in Sleipner, in the North Sea, millions of tons of carbon dioxide have been injected into a sandstone geological reservoir in the past fifteen years, where CO2 is stored in liquid form. CO2 can also be stored in solid form through mineralization processes, minimising the risk of leakage. Small-scale ongoing projects, such as Carbfix in Iceland, show promising results but questions of efficiency remain.

“The natural process is very effective but too slow, so we wonder whether we could somehow accelerate it so that large quantities of CO2 could be injected underground, without leakage”, explains François Renard, director of the Njord Centre at the University of Oslo and ESRF user.

The natural process

Atmospheric CO2 and water from precipitations naturally react with rocks present at the Earth’s surface – this process is called weathering. Some of these rocks have been produced by volcanic activity (basalts in Iceland) or were exhumed to the Earth’s surface from the mantle (peridotites). When reacting with CO2 and water, they may dissolve partially over geological time scales, liberating magnesium, iron, and calcium ions that can bind with carbon dioxide, in a process called mineral carbonation, which converts CO2 into minerals. The end product is a calcium, iron or magnesium carbonate, which are stable minerals that effectively trap carbon dioxide into a solid form.

Renard and his team are focusing on storing CO2 in basaltic and peridotite rocks, rich in magnesium and calcium, as they are the most efficient environments for it due to their high reactivity. They make up about 70% of the Earth’s surface and are responsible for 1/3 of the trapping of CO2 from the atmosphere through weathering. Estimates suggest that mid-ocean ridges worldwide can store up to 100,000 Gt of CO2. This is more than 2000 times the annual global emissions of CO2.

Once in the basaltic or peridotite rocks, the CO2 quickly reacts with the divalent cations (Ca2+, Mg2+, and Fe2+) from dissolving minerals in the rock and form carbonate minerals. In comparison, it might take several tens of thousands of years for significant amounts of CO2 to mineralize in a sandstone reservoir. After it becomes a mineral, the carbon will not move over geological timescales.

Carbonation at the ESRF

The team is focused on studying how basalts and peridotites can host large quantities of flows of carbon dioxide mixed with water, which will react with the rock to produce carbonate minerals. 

Read more on ESRF website

High-pressure synthesis of carbonic acid polymorphs from carbon dioxide clathrate hydrate

High-pressure synthesis of carbonic acid polymorphs from carbon dioxide clathrate hydrate

Carbon dioxide (CO2) is largely present in diverse astrochemically relevant environments, quite often co-existing with water (H2O) ices. Their simultaneous presence has triggered a great interest regarding the stabilization of CO2 clathrate hydrates and the possible formation of adducts under various thermodynamic conditions. Amongst these adducts, solid carbonic acid (H2CO3) remains elusive. All the synthetic routes followed up to now for its production required quite drastic conditions (from high energy protonation of solid CO2 to laser heating at high pressure on fluid mixtures of CO2 and H2O).

In our study, we discovered a highly reproducible, simpler and effective way to synthesize two diverse carbonic acid crystal structures upon the fast, cold compression of pristine CO2 clathrate hydrates. We found that the products of this reaction strictly depend on the starting pressures, resulting in three different reaction pathways. In the first pathway, for pressures lower than 2.7 GPa, pristine CO2 clathrate hydrate simply decomposes into its constituents, as expected from previous studies. For intermediate pressures (between 2.7 and 4.8 GPa), a first crystalline phase is observed, characterized by a well-defined lattice phonon region (see Figure 1a, green spectrum) and a specific diffraction pattern. For pressures exceeding 4.8 GPa, the formation of an amorphous product is observed, characterized by a broad, unstructured band in the lattice phonon region (see Figure 1a, black spectrum). Both the two products feature an intense, quite broad Raman band at about 1050 cm-1, a reported signature band for carbonate-based systems and, also, carbonic acid (see Figure 1b). We found that the high pressure, amorphous product (called a-ε) transformed upon decompression down to 4.8 GPa or heating at higher pressures into a distinct, much more structured crystalline phase characterized by 10 lattice phonons (see Figure 1a, red spectrum) and sharper internal Raman bands (Figure 1b, red spectrum). This structure was found to be that already reported by Abramson and co-authors in a recent paper, where it was obtained in much more drastic conditions (from fluid CO2 and H2O upon resistive heating): we called this phase ε-H2CO3.

Read more on Elettra website

Conversion of carbon dioxide into raw materials more effective with gold

Conversion of carbon dioxide into raw materials more effective with gold

Carbon dioxide, emitted mainly by combustion of fossil fuels, is harmful to the climate and the main reason for increased global warming. Diverting carbon dioxide into hydrogen carriers or chemicals such as methanol, a valuable raw material and energy carrier, is thus highly desired. Supported metal nanoparticle heterogeneous catalysts such as copper on zinc oxide is used for the catalytic conversion of carbon dioxide to methanol. Researchers have now discovered that it is possible to avoid by-products and at the same time make the process more sustainable by adding a small amount of gold to the catalyst.

Carbon dioxide can be converted into methanol and water by reaction with hydrogen. The reaction is only possible in the presence of a catalytic material such as Au or Cu nanoparticles supported on zinc oxide. The chemical reaction will then take place on the particle surfaces. In a recent study, a research team from Germany, Japan and Sweden have shown that modifying the typical ZnO-supported Cu nanoparticles by a small amount of gold (< 10 weight percent) makes the reaction more selective.

Read more on MAX IV website

Building a better carbon capture system

Building a better carbon capture system

Carbon capture has been hailed as a ground-breaking technology for cleaning the air. And it is, but there are some drawbacks – it’s expensive, and most technology requires the generation and application of heat, which creates emissions.

There had to be a better way, thought Dr. Haotian Wang, associate professor in the Department of Chemical and Biomolecular Engineering at Rice University at Houston, Texas.

Wang and his team found it in a process of electrolysis they studied at Rice and collaborated on with the Canadian Light Source (CLS) at the University of Saskatchewan. They have devised a modular solid electrolyte reactor that, in time, will be usable everywhere, in industry but also for “household use, small business use, space station, submarine, any enclosed environment,” he said. Their study was published in the journal Nature.

“Our new approach is integrated capture and regeneration, which means that you can continuously concentrate the carbon dioxide from dilute sources into almost 100 percent purity.”

The reactor is divided into three chambers. Electrolysis, a process by which electric current is passed through a substance to effect a chemical change, occurs on two sides — one performing oxygen reduction and the other oxygen evolution. The oxygen reduction reaction creates an alkaline environment, which captures carbon and then releases it in the central chamber.

The carbon can either be stored underground or converted to valuable products such as alcohols, “which is also an important direction we are working on,” Wang said.

Crucially, no chemical inputs other than water are required and no side products are generated.

Wang has estimated that the cost of capturing carbon will be $83 per ton, but with improvements, that could drop to $58 or even $33 per ton, a big saving from today’s costs, which range from $125 to $600 USD.

“It’s not only the cost but also the energy source that we can use, which is electricity,” he said. “Ideally, we want to transform this into an electrifying process because in the future we can get a lot (of clean electricity) from solar farms, wind farms and nuclear power plants.”

The CLS played an important role in this work.

Read more on the CLS website

Understanding How the Structure of Boron Oxynitride Affects its Photocatalytic Properties

Understanding How the Structure of Boron Oxynitride Affects its Photocatalytic Properties

Synchrotron studies show that tuning the synthesis of boron oxynitride can improve its performance as a photocatalyst and semiconductor

Carbon dioxide (CO2) is often in the news these days. As a greenhouse gas, released during the combustion of fossil fuels, it is fuelling climate change, and reducing our CO2 emissions is critical to a sustainable future. CO2 is also a by-product of many industrial processes, including the production of ammonia used for fertilisers. On the other hand, many industries need a regular supply of CO2, and shortages have caused problems in recent years. It makes sense, therefore, to find ways to recycle some of the waste CO2 we produce into useful products. However, CO2 conversion reactions are energy-intensive, and new catalysts are needed to make the reactions more efficient. Photocatalysts absorb light energy, creating a charge separation that can then drive a chemical reaction. A team of researchers from Imperial College London are researching CO2 conversion using photocatalysis. In work recently published in Chemistry of Materials, they investigated how oxygen doping affects the photocatalytic and optoelectronic properties of boron nitride. Their results provide valuable insights into the photochemistry of boron oxynitride (BNO) at the fundamental level.

By clarifying the importance of paramagnetism in BNO semiconductors and providing fundamental insight into their photophysics, this study paves the way to tailoring its properties for CO2 conversion photocatalysis. The group has also recently used a similar methodology to investigate phosphorus doping of boron nitride, which they will explore in a future publication. 

Read more on the Diamond Light Source website

Image: Combined experimental (EPR, NEXAFS) + computational study (DFT)

Credit: Image via Chem. Mater. 2023, 35, 5, 1858-1867

Synthesised a new catalyst with key properties to solve environmental issues

Synthesised a new catalyst with key properties to solve environmental issues

A research led by the ITQ-CSIC-UPV has discovered a new catalyst enabling hydrogenation of carbon dioxide to methane with advantages not seen until now. This new catalyst, whose structure and mechanism have been understood by synergistically exploiting different ALBA Synchrotron techniques, can be used for methane (natural syngas) production, that is considered as a promising energy carrier for hydrogen storage.

Linear economy has proven to be unsustainable in the long run due to its ineffective use of natural resources that leads to a huge amount of greenhouse gas emissions and waste generation. An alternative model, the so-called circular economy is based on an efficient production cycle that focuses on minimising waste and better recycling and seems to be key to find solutions for the climate crisis. One process that can be essential in this challenge is carbon dioxide (CO2) sequestration and usage, that is, transform atmospheric or produced carbon dioxide into energy carriers or platform molecules of the chemical industry.

An international collaboration between the Instituto de Tecnología Química – a join research center between Consejo Superior de Investigaciones Científicas and Universitat Politècnica de València (ITQ-CSIC-UPV), SOLEIL Synchrotron, Universidad de Cádiz, and ALBA Synchrotron permitted to synthesize a new catalyst able to hydrogenate carbon dioxide to methane with significant improvements in comparison to existing analogues. Its main advantage is that it possesses a much higher activity and so the reaction temperature can be lowered from usual 270-400ºC to only 180ºC, with an excellent long-term stability. Furthermore, this catalyst is able to operate under intermittent power supply conditions, which couples very well with electricity production systems based on renewable energies. Moreover, its synthetic procedure itself is ecofriendly, making it an even greater option in environmental issues.

This new catalyst can be used for methane (natural syngas) production, that is considered as a promising energy carrier for hydrogen storage.

The new solid catalyst was designed and synthesized in the ITQ (CSIC-UPV) by a mild, green hydrothermal synthesis procedure resulting in a material that contains interstitial carbon atoms doped in the ruthenium (Ru) oxide crystal lattice, enabling the stabilization of Ru cations in a low oxidation state with the formation of a none yet reported ruthenium oxy-carbonate phase.

Read more on ALBA website

How a record-breaking copper catalyst converts CO2 into liquid fuels

How a record-breaking copper catalyst converts CO2 into liquid fuels

Researchers at Berkeley Lab, collaborating with CHESS scientists at the PIPOXS beamline, have made the first real-time movies of copper nanoparticles as they evolve to convert carbon dioxide and water into renewable fuels and chemicals. Their new insights could help advance the next generation of solar fuels.

Since the 1970s, scientists have known that copper has a special ability to recycle carbon dioxide into valuable chemicals and fuels. But for many years, scientists have struggled to understand how this common metal works as an electrocatalyst, a mechanism that uses energy from electrons to chemically transform molecules into different products.

Now, a research team led by Lawrence Berkeley National Laboratory (Berkeley Lab) has gained new insight by capturing the world’s first real-time movies of copper nanoparticles (copper particles engineered at the scale of a billionth of a meter) as they convert CO2 and water into renewable fuels and chemicals: ethylene, ethanol, and propanol, among others. The work was reported in the journal Nature.

“This is very exciting. After decades of work, we’re finally able to show – with undeniable proof – how copper electrocatalysts excel in CO2 reduction,” said Peidong Yang, a senior faculty scientist in Berkeley Lab’s Materials Sciences and Chemical Sciences Divisions who led the study. Yang is also a professor of chemistry and materials science and engineering at UC Berkeley. “Knowing why copper is such an excellent electrocatalyst brings us steps closer to turning CO2 into new, renewable solar fuels through artificial photosynthesis.”

Read more on the CHESS website

Image: Artist’s rendering of a copper nanoparticle as it evolves during CO2 electrolysis: Copper nanoparticles (left) combine into larger metallic copper “nanograins” (right) within seconds of the electrochemical reaction, reducing CO2 into new multicarbon products.

Credit: Yao Yang/Berkeley Lab

Electrocatalysis – Iron and Cobalt Oxyhydroxides examined

Electrocatalysis – Iron and Cobalt Oxyhydroxides examined

A team led by Dr. Prashanth W. Menezes (HZB/TU-Berlin) has now gained insights into the chemistry of one of the most active anode catalysts for green hydrogen production. They examined a series of Cobalt-Iron Oxyhydroxides at BESSY II and were able to determine the oxidation states of the active elements in different configurations as well as to unveil the geometrical structure of the active sites. Their results might contribute to the knowledge based design of new highly efficient and low cost catalytical active materials.

Very soon, we need to become fossil free, not only in the energy sector, but as well in industry. Hydrocarbons or other raw chemicals can be produced in principle using renewable energy and abundant molecules such as water and carbon dioxide with the help of electrocatalytically active materials. But at the moment, those catalyst materials either consist of expensive and rare materials or lack efficiency.

Key reaction in water splitting

A team led by Dr. Prashanth W. Menezes (HZB/TU-Berlin) has now gained insights into the chemistry of one of the most active catalysts for the anodic oxygen evolution reaction (OER), which is a key reaction to supply electrons for the hydrogen evolution reaction (HER) in water splitting. The hydrogen can then be processed into further chemical compounds, e.g., hydrocarbons. Additionally, in the direct electrocatalytic carbon dioxide reduction to alcohols or hydrocarbons, the OER also plays a central role.

Read more on the HZB website

Image: LiFex-1Cox Borophosphates have been used as inexpensive anodes for the production of green hydrogen. Their dynamic restructuring during OER as well as their catalytically active structure, have been elucidated via  X-ray absorption spectroscopy.

Credit: © P. Menezes / HZB /TU Berlin

How a soil microbe could rev up artificial photosynthesis

How a soil microbe could rev up artificial photosynthesis

Researchers discover that a spot of molecular glue and a timely twist help a bacterial enzyme convert carbon dioxide into carbon compounds 20 times faster than plant enzymes do during photosynthesis. The results stand to accelerate progress toward converting carbon dioxide into a variety of products.

Plants rely on a process called carbon fixation – turning carbon dioxide from the air into carbon-rich biomolecules ­– for their very existence. That’s the whole point of photosynthesis, and a cornerstone of the vast interlocking system that cycles carbon through plants, animals, microbes and the atmosphere to sustain life on Earth. 

But the carbon fixing champs are not plants, but soil bacteria. Some bacterial enzymes carry out a key step in carbon fixation 20 times faster than plant enzymes do, and figuring out how they do this could help scientists develop forms of artificial photosynthesis to convert the greenhouse gas into fuels, fertilizers, antibiotics and other products.

Now a team of researchers from the Department of Energy’s SLAC National Accelerator Laboratory, Stanford University, Max Planck Institute for Terrestrial Microbiology in Germany, DOE’s Joint Genome Institute (JGI) and the University of Concepción in Chile has discovered how a bacterial enzyme – a molecular machine that facilitates chemical reactions – revs up to perform this feat.

Rather than grabbing carbon dioxide molecules and attaching them to biomolecules one at a time, they found, this enzyme consists of pairs of molecules that work in sync, like the hands of a juggler who simultaneously tosses and catches balls, to get the job done faster. One member of each enzyme pair opens wide to catch a set of reaction ingredients while the other closes over its captured ingredients and carries out the carbon-fixing reaction; then, they switch roles in a continual cycle.  

Read more on the SLAC website

Helping to neutralise greenhouse gases

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.