Harvard University researchers have devised a catalyst that uses renewable electricity to electrochemically transform carbon dioxide into carbon monoxide (CO). CO is a key commodity used in a large number of industrial processes.

For Haotian Wang, it’s the perfect raw material. Wang, a Fellow at the Rowland Institute at Harvard, and his research team have developed a system that uses renewable electricity supplies, with energy conversion efficiency from sunlight to CO that can be as high as 12.7 %, more than one order of magnitude higher than natural photosynthesis.

The Harvard team’s device is described in an recent paper published in Chem.

Wang explained, “Basically, what this is is a form of artificial photosynthesis. In a plant, sunlight, CO2 and water become sugar and oxygen. In our system, the input is sunlight, CO2 and water, and we produce CO and oxygen.”

That reaction takes place in an unassuming-looking device, barely the size of a smartphone, that includes two electrolyte-filled chambers separated by an ion exchange membrane.

On one site, an electrode powered by renewable energy oxidizes water molecules into oxygen gas and frees protons. These protons move to the other chamber where – with the help of a carefully designed metal single atom catalyst – they bind to carbon dioxide molecules, creating water and carbon monoxide.

Wang continued, “The challenge is that most catalysts that are known tend to produce hydrogen gas. So it’s difficult, when you split water, to prevent those protons from combining together to form hydrogen gas. What we needed was a catalyst that can prevent hydrogen evolution and instead can efficiently inject those protons into CO2, therefore achieving a high selectivity for CO2 reduction.”

Unfortunately, the two best-known such catalysts are gold and silver, precious metals that are very costly to make the reaction cost effective on a large scale.

Kun Jiang said, who is a postdoctoral fellow in Wang group and the first author of this work takes up the description, “So we began by looking at low-cost materials like nickel, iron and cobalt, which are all Earth-abundant. But the problem is that they are all very good hydrogen catalysts, so they want to produce hydrogen gas.

In addition, they can all very easily be poisoned by carbon monoxide,” he added. “Even if you manage to use them to reduce CO2, the resulting CO bonds very strongly to the surface, preventing any further reactions from taking place.”

To solve those problems, Wang and his Stanford collaborators, Prof. Yi Cui and Prof. Jens Nørskov, set about working to “tune” the electronic properties of the metals. Dr. Samira Siahrostami, a staff scientist from Prof. Nørskov group rationalized the nature of active sites by atomic scale modeling and discovered that dispersing nickel metals into isolated single atoms, which are trapped in graphene vacancies, produced a material that was eager to react with carbon dioxide and willing to release the resulting carbon monoxide.

That carbon monoxide, Wang said, can then be used in a host of industrial processes.

“Carbon monoxide is a very important industry product,” Wang said. “It can be used in plastics production, to make hydrocarbon products or can be burned as a fuel itself. It’s widely used in industry.”

Ultimately, though, the hope is that the system could one day be scaled up enough to scrub carbon dioxide from the atmosphere in an effort to combat global climate change.

“The basic idea was if we can capture existing CO2 and use renewable electricity, from solar or wind power, to reduce it into useful chemicals,” Wang said, “then we can possibly form a carbon loop.”

This looks like an important addition to the CO2 question. While the global warming crowd isn’t keeping up with the dissolution of their theory, CO2 has value and catching and recycling it is a worthwhile enterprise particularly in products and over time in getting humans is tune with the planet’s carbon cycle.

Lets Recycle CO2!

December 6, 2017 | 3 Comments

Korea’s Daegu Gyeongbuk Institute of Science and Technology (DGIST) research team has developed titanium dioxide-based photocatalyst with the highest efficiency in the world that converts carbon dioxide recycling it into methane. The result is expected to be applied to technologies to reduce and reuse carbon dioxide. The team’s titanium dioxide (TiO2) -based high efficiency photocatalyst converts carbon dioxide to methane using a simple reduction method.

Its asserted by some scientists that anthropogenic emission of greenhouse gases, particularly CO2, is a significant factor driving global climate change. The clamor is pushing for sustainable, low carbon, readily portable fuels. For that goal there has been a worldwide effort underway to find ways to convert carbon dioxide into a usable fuel, such as hydrogen, methane, ethanol, methanol, and butanol.

The study paper has been published in the online edition of Materials Today, the international journal of materials science.

A graphic methane photocatalyst comparison. Image Credit: Daegu Gyeongbuk Institute of Science and Technology. Click image for the largest view.

In order to utilize carbon dioxide as a resource, it is essential to increase the conversion efficiency and light absorption efficiency when converting carbon dioxide into fuel, and to make photocatalyst help in preventing secondary harmful substances.

High-efficiency photocatalyst development technology that synthesizes materials such as titanium dioxide, copper oxide, and reduced graphene oxide, or controls the structure and surface of photocatalyst material is regarded as the core of carbon dioxide recycling technology.

Surprisingly, DGIST’s research team has discovered a synthesis method which rapidly reduces TiO2 at low temperatures using a strong reducing agent, sodium borohydride (NaBH4).

In the study, titanium dioxide-based photocatalysts using this synthesis method showed 12.49% conversion of methane to photochemical carbon dioxide on the gas phase, which represents the highest conversion rate among the introduced photocatalysts so far.

Additionally, the photocatalyst developed by the research team has the controlled band gap through the conversion of the oxidation number from 4 to 3 by breaking the oxygen atoms on the surface of titanium dioxide. This change increases the amount of light absorption and efficiently separates the charge, resulting in higher carbon conversion of carbon dioxide. Moreover, the experiment has also proved that the efficiency of methane conversion of carbon dioxide can be increased up to 29 times using platinum nanoparticles.

Professor In, the corresponding author stated, “The newly developed titanium dioxide photocatalyst is superior to the other photocatalysts reported so far as it has outstanding carbon dioxide conversion efficiency as well as excellent stability.” He also mentioned, “We would like to contribute to the development of carbon dioxide reduction and recycling technology by conducting further researches to improve conversion efficiency to the extent that it can be commercialized.”

The press release labors under the global warming banner with plenty of associations in a field that justifies its progress on its own. Recycling CO2, putting the human species in tune with the planet’s carbon cycle is easily reason enough with out the global warming thing burdening the effort.

Kyushu University scientists have synthesized a compound that absorbs near-infrared light to produce hydrogen from water. The compound contains three ruthenium atoms connected by an organic molecule. The absorbed light stimulates electrons to ‘jump’ into orbitals that do not exist in other, similar compounds. This is the first successful use of infrared light to reduce water into hydrogen, which can be used for energy conversion and storage, and other industrial purposes in a future sustainable energy society.

Image Credit: Kyushu University, Institute for Carbon-Neutral Energy Research. Click image for the largest view.

Hydrogen gas is a promising “green” fuel. The lightest chemical element, hydrogen is an efficient energy store and could potentially replace gasoline in vehicles. But the element does not exist in large amounts in nature, and must be produced artificially.

Sunlight comes in a spectrum, with each color having a different wavelength. Solar cells must absorb light of particular wavelengths, depending on how much energy the cell needs to drive the reaction. The more of the spectrum it captures, the more hydrogen it produces. Unfortunately, most cells only absorb shorter wavelengths of light, corresponding to the higher energy region of visible light below the red light domain. This means that while colors such as blue and green light can be used, the rest is wasted.

The researchers at Kyushu University in Japan and its Institute for Carbon-Neutral Energy Research (I2CNER) may have potentially solved this problem. They invented a device driven by near-infrared (NIR) light – the part of the spectrum, invisible to the naked eye, with wavelengths longer than visible red light. Thus, they enabled a broader spectrum of light, including UV, visible, and NIR, to be harvested. Their design cleverly exploits the chemistry of ruthenium, a heavy metal related to iron.

The achievement research report has been published in Angewandte Chemie International Edition.

Particular metal-organic hybrid materials are good at capturing light, which helps their electrons to “jump” into orbitals in the organic parts of the materials attached to the metal center. In solar cells, this is the first step in producing hydrogen, since electrons are the drivers of chemistry. However, the jump between orbitals is usually so big that only UV and the higher energy region of visible light have enough energy to stimulate it. Red, NIR, and even longer IR light are simply reflected back or pass through the devices, and their energy remains unused.

The Kyushu design is different. Study corresponding author Professor Ken Sakai explained, “We introduced new electron orbitals into the ruthenium atoms. It’s like adding rungs to a ladder – now the electrons in ruthenium don’t have so far to jump, so they can use lower energies of light such as red and NIR. This nearly doubles the amount of sunlight photons we can harvest.”

The trick is to use an organic compound – hexagonal rings of carbon and nitrogen – to link three metal atoms into a single molecule. In fact, this not only creates these new “rungs” – hence the ability to use red and NIR light – but also makes the reaction more efficient due to spatial expansion of the light harvesting part of the molecule. Thus, the production of hydrogen is accelerated.

Sakai said, “It’s taken decades of efforts worldwide, but we’ve finally managed to drive water reduction to evolve H2 using NIR. We hope this is just the beginning – the more we understand the chemistry, the better we can design devices to make clean, hydrogen-based energy storage a commercial reality.”

This research looks like a good addition to the other efforts. Perhaps an engineer will be able to tie the full spectrum of sunlight into a working water splitting module. Lets hope they stay the course and refine the concept into a pilot ready process.

University of Toronto Faculty of Applied Science & Engineering researchers new catalyst is one step closer to artificial photosynthesis. It is a system that, just like plants, would use renewable energy to convert recycle carbon dioxide (CO2) into stored chemical energy. By both capturing carbon emissions and storing energy from solar or wind power, the invention provides a one-two punch in the fight battle to find new sources of non fossil fuels.

Phil De Luna, one of the lead authors of a paper published today in Nature Chemistry said, “Carbon capture and renewable energy are two promising technologies, but there are problems. Carbon capture technology is expensive, and solar and wind power are intermittent. You can use batteries to store energy, but a battery isn’t going to power an airplane across the Atlantic or heat a home all winter: for that you need fuels.”

De Luna and his co-lead authors Xueli Zheng and Bo Zhang – who conducted their work under the supervision of Professor Ted Sargent – aim to address both challenges at once, and they are looking to nature for inspiration. They are designing an artificial system that mimics how plants and other photosynthetic organisms use sunlight to convert CO2 and water into molecules that humans can later use for fuel.

Like plants, their system consists of two linked chemical reactions: one that splits H2O into protons and oxygen gas, and another that converts CO2 into carbon monoxide, or CO. (The CO can then be converted into hydrocarbon fuels through an established industrial process called Fischer-Tropsch synthesis.)

Schematic illustration of the in situ liquid cell experimental set-up. Image Credit: University of Toronto Faculty of Applied Science & Engineering. Click image for the largest view.

Zhang, who contributed to the work while a post-doctoral fellow at U of T and is now a professor at Fudan University said, “Over the last couple of years, our team has developed very high-performing catalysts for both the first and the second reactions. But while the second catalyst works under neutral conditions, the first catalyst requires high pH levels in order to be most active.”

That means that when the two are combined, the overall process is not as efficient as it could be, as energy is lost when moving charged particles between the two parts of the system.

The team has now overcome this problem by developing a new catalyst for the first reaction – the one that splits water into protons and oxygen gas. Unlike the previous catalyst, this one works at neutral pH, and under those conditions it performs better than any other catalyst previously reported.

Zheng, who is now a postdoctoral scholar at Stanford University added, “It has a low overpotential, which means less electrical energy is needed to drive the reaction forward. On top of that, having a catalyst that can work at the same neutral pH as the CO2 conversion reaction reduces the overall potential of the cell.”

In the paper, the team reported the overall electrical-to-chemical power conversion efficiency of the system at 64 percent. According to De Luna, this is the highest value ever achieved for such a system, including their previous one, which only reached 54 per cent.

The new catalyst is made of nickel, iron, cobalt and phosphorus, all elements that are low-cost and pose few safety hazards. It can be synthesized at room temperature using relatively inexpensive equipment, and the team showed that it remained stable as long as they tested it, a total of 100 hours.

Armed with their improved catalyst, the Sargent lab is now working to build their artificial photosynthesis system at pilot scale. The goal is to capture CO2 from flue gas – for example, from a natural gas-burning power plant – and use the catalytic system to efficiently convert it into liquid fuels.

De Luna explained, “We have to determine the right operating conditions: flow rate, concentration of electrolyte, electrical potential. From this point on, it’s all engineering.”

The team and their invention are semi-finalists in the NRG COSIA Carbon XPRIZE, a $20 million challenge to “develop breakthrough technologies that will convert CO2 emissions from power plants and industrial facilities into valuable products.”

The project was the result of an international and multidisciplinary collaboration. The Canadian Light Source in Saskatchewan provided the high-energy x-rays used to probe the electronic properties of the catalyst. The Molecular Foundry at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory did theoretical modeling work. Financial and in-kind support were provided by the Natural Sciences and Engineering Research Council, the Canada Foundation for Innovation, Tianjin University, Fudan University and the Beijing Light Source.

As for what has kept him motivated throughout the project, De Luna points to the opportunity to make an impact on some of society’s biggest environmental challenges.

“Seeing the rapid advancement within the field has been extremely exciting,” he said. “At every weekly or monthly conference that we have within our lab, people are smashing records left and right. There is still a lot of room to grow, but I genuinely enjoy the research, and carbon emissions are such a big deal that any improvement feels like a real accomplishment.”

For now oil is very low cost. But we all know that won’t last. Next time oil rockets up one or more of these ideas will find their foothold on the future. One hopes the economy can weather the transition. It will take decades to make the switch.

UCLA Scientists have developed a 2-in-1 device that uses supercapacitor to store energy and spit hydrogen from water.

The device could make hydrogen cars affordable for many more consumers because it produces hydrogen using nickel, iron and cobalt — elements that are much more abundant and less expensive than the platinum and other precious metals that are currently used to produce hydrogen fuel.

Replica example of the new energy storage and conversion device designed at UCLA. Image Credit: University of California Los Angeles. Click image for the largest view.

Richard Kaner, the study’s senior author and a UCLA distinguished professor of chemistry and biochemistry, and of materials science and engineering said, “Hydrogen is a great fuel for vehicles: It is the cleanest fuel known, it’s cheap and it puts no pollutants into the air — just water. And this could dramatically lower the cost of hydrogen cars.”

The technology, described and published in the journal Energy Storage Materials, could be especially useful in rural areas, or to military units serving in remote locations.

“People need fuel to run their vehicles and electricity to run their devices,” Kaner said. “Now you can make both electricity and fuel with a single device.”

It could also be part of a solution for large cities that need ways to store surplus electricity from their electrical grids.

“If you could convert electricity to hydrogen, you could store it indefinitely,” said Kaner, who also is a member of UCLA’s California NanoSystems Institute.

Traditional hydrogen fuel cells and supercapacitors have two electrodes: one positive and one negative. The device developed at UCLA has a third electrode that acts as both a supercapacitor, which stores energy, and as a device for splitting water into hydrogen and oxygen, a process called water electrolysis. All three electrodes connect to a single solar cell that serves as the device’s power source, and the electrical energy harvested by the solar cell can be stored in one of two ways: electrochemically in the supercapacitor or chemically as hydrogen.

The device also is a step forward because it produces hydrogen fuel in an environmentally friendly way. Currently, about 95 percent of hydrogen production worldwide comes from converting fossil fuels such as natural gas into hydrogen — a process that releases large quantities of carbon dioxide into the air, said Maher El-Kady, a UCLA postdoctoral researcher and a co-author of the research.

“Hydrogen energy is not ‘green’ unless it is produced from renewable sources,” El-Kady said. He added that using solar cells and abundantly available elements to split water into hydrogen and oxygen has enormous potential for reducing the cost of hydrogen production and that the approach could eventually replace the current method, which relies on fossil fuels.

Combining a supercapacitor and the water-splitting technology into a single unit, Kaner said, is an advance similar to the first time a phone, web browser and camera were combined on a smartphone. The new technology may eventually lead to new applications that even the researchers haven’t considered yet, Kaner said.

The researchers designed the electrodes at the nanoscale — thousands of times thinner than the thickness of a human hair — to ensure the greatest surface area would be exposed to water, which increases the amount of hydrogen the device can produce and also stores more charge in the supercapacitor. Although the device the researchers made would fit in the palm of your hand, Kaner said it would be possible to make larger versions because the components are inexpensive.

“For hydrogen cars to be widely used, there remains a need for a technology that safely stores large quantities of hydrogen at normal pressure and temperature, instead of the pressurized cylinders that are currently in use,” said Mir Mousavi, a co-author of the paper and a professor of chemistry at Iran’s Tarbiat Modares University.

The paper’s other co-authors are graduate student Yasin Shabangoli and postdoctoral scholars Abolhassan Noori and Mohammad Rahmanifar, all of Tarbiat Modares.

One day one of these ideas is going to economically irresistible. This looks like a big step that way with two processes in a small box. Its getting closer. We still have to find that hydrogen storage miracle.


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