New battery gobbles up carbon dioxide

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According to Phys.org (This article and its images were originally posted on Phys.org September 21, 2018 at 01:51PM.)

(Cover Image)

This scanning electron microscope image shows the carbon cathode of a carbon-dioxide-based battery made by MIT researchers, after the battery was discharged. It shows the buildup of carbon compounds on the surface, composed of carbonate material that could be derived from power plant emissions, compared to the original pristine surface (inset). Credit: Massachusetts Institute of Technology

A new type of battery developed by researchers at MIT could be made partly from carbon dioxide captured from power plants. Rather than attempting to convert carbon dioxide to specialized chemicals using metal catalysts, which is currently highly challenging, this battery could continuously convert carbon dioxide into a solid mineral carbonate as it discharges.

While still based on early-stage research and far from commercial deployment, the new battery formulation could open up new avenues for tailoring electrochemical carbon dioxide conversion reactions, which may ultimately help reduce the emission of the greenhouse gas to the atmosphere.

 

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This article and its images were originally posted on [Phys.org] September 21, 2018 at 01:51PM. Credit to the original author and Phys.org | ESIST.T>G>S Recommended Articles Of The Day.

 

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‘Super-dry’ reforming reaction converts greenhouse gases to useful intermediates

(Phys.org)—A new “super-dry” carbon dioxide reforming reaction consumes two waste products, carbon dioxide and methane, and produces gases that can be used to make synthetic fuels and other important products.

Researchers from Ghent University in Belgium, led by Dr. Vladimir Galvita have developed a nickel-catalyzed carbon reforming reaction scheme that involves the use of calcium oxide as a carbon dioxide sorbent and iron oxide as a solid oxygen carrier. This process does not involve temperature swings, allowing for better carbon monoxide production, and their two-flow system eliminates unwanted back reactions. Their work appears in a recent issue of Science.

In an effort to decrease CO₂ production, scientists have developed methods to convert CO₂ to helpful starting materials that can be used to produce synthetic energy sources. These methods involve reducing CO₂. The most commercially feasible method is a process called dry reforming of methane, which produces syngases, CO and H₂. This reaction needs to be a “dry” reaction because in the presence of water, the more energetically favored water gas shift reaction occurs. In this reaction carbon monoxide reacts with water to re-form carbon dioxide. Eliminating water from these reactions has proved to be an active area of research.

In the current study, Buelens et al. used calcium oxide as a CO₂ sorbent in which calcium carbonate is formed. This has several benefits that that has allowed a higher carbon monoxide yield and an opportunity to remove water that is formed from the oxidation of methane.

First, from an economic and practical standpoint, because CO₂ is removed in situ, the feed gas can be of lower stock quality. Secondly, the formation of calcium carbonate can be coupled with methane reformation and iron oxide reduction resulting in a more energetically favorable process. Then, when calcium carbonate decomposes into CO₂ and CaO, the carbon dioxide is reduced to CO over the iron oxide oxygen carrier. According to the authors, it is at this point that the feed is switched to inert gas to regenerate the system.

They obtained a 45% higher CO yield, but this yield could be even higher by optimizing conditions. The higher efficiency of this reaction is due in large part by employing Le Chatlier’s Principle.

Importantly, their two-flow reaction set-up seems to have some versatility that prior dry reforming reactions lacked either by changing the gas feedstock ratios or by changing to a multi-reactor configuration.

The applications of this technique, according to lead author, Lukas Buelens is that “with this process, we intensify the conversion of CO₂ by making maximal use of CH₄ as reducing gas. The generated CO can be used directly or combined with a green H₂ source for the production of chemicals or fuels.”

Additionally, their initial flow system uses a less expensive nickel catalyst because carbon deposition has been eliminated. Their system is more efficient for CO₂ utilization than prior dry reforming reactions and may serve as a model for optimized CO₂ conversion.

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It’s official: the world has agreed to phase out dangerous heat-trapping HFCs

Almost 200 nations have struck a historical climate deal that will phase out the use of one of the world’s most potent greenhouse gases, hydrofluorocarbons(HFCs).

In an amendment to the Montreal Protocol – endorsed on Saturday in Kigali, Rwanda by 197 signatories – countries will begin to reduce their usage of HFCs by 2019.

This represents the most decisive action yet to honour the commitments of the United Nations Climate Change Conference in Paris last year.

While the Rwanda agreement hasn’t scored the same global headlines as the Paris accord, it’s a huge deal that took some seven years of negotiations to hammer out. And its specific target of phasing out HFCs alone will make it easier to enforce and police than the more generalised commitments made in 2015.

“It is likely the single most important step we could take at this moment to limit the warming of our planet and limit the warming for generations to come,” US Secretary of State John Kerry told fellow negotiators in Kigali. “It is the biggest thing we can do in one giant swoop.”

Whereas the focus of the Paris deal was on setting national limits on carbon dioxide (CO2) output to help limit the rise in average global temperatures over the course of the century, the new amendment is narrowly focused on phasing out HFCs in the near term.

These coolants are used in refrigerators and air conditioners, and although they only make up a small fraction of greenhouse gases in the atmosphere overall, they’re the fastest growing kind – increasing by up to 10 percent each year, due to the uptake of cooling devices in developing countries.

Worse still, HFCs are particularly dangerous to the environment from a thermal perspective, because they can trap thousands of times more heat than CO2.

Ironically, we can thank the Montreal Protocol for HFCs existing in the first place. They were originally developed in reaction to the 1987 agreement, which sought to ban chlorofluorocarbons (CFCs) – chemicals that deplete the ozone layer.

Under the new amendment, developed countries will start to phase down HFCs by 2019. A group of more than 100 developing countries, including China, will have to cap their use by 2024, before beginning reductions later. And a smaller group of nations, including India and Pakistan, will commence capping in 2028.

It’s estimated that the agreement could see global HFC use reduced by up to 85 percent by 2047, with scientists saying the reduction will remove the equivalent of about 70 billion tonnes of CO2 from the atmosphere by 2050.

To put the scale of this in perspective, the reduction is about “equal to stopping the entire world’s fossil fuel CO2 emissions for more than two years,” air pollution expert David Doniger from the New York-based Natural Resources Defence Council told The Guardian.

But while it’s a huge step forward in reducing the amount of this powerful heat-trapping chemical in the atmosphere, the agreement doesn’t go as far as environmentalists wanted.

Environmental groups had argued for an HFCs deal that would reduce global warming by 0.5 degrees Celsius by the end of this century. As it stands, the Kigali amendment is estimated to only reduce temperature rises by a maximum of 0.44 degrees Celsius.

Still, that’s not too bad, given it would nonetheless represent the largest temperature reduction ever achieved by a single agreement.

“We came to take a half a degree Celsius out of future warming, and we won about 90 percent of our climate prize,” said Durwood Zaelke of the Institute for Governance & Sustainable Development.

“The majority of the low-hanging fruit has been picked with this amendment, and we’ll get the rest through market forces.”

Those market forces include incentives for countries that cut back on HFCs sooner, as well as grants for the research and development of new chemicals that can take the place of HFCs in cooling devices, much like HFCs once replaced CFCs.

Another reason to be encouraged is the legal force of the new deal.

This is “much, much, much stronger than Paris”, Zaelke told Coral Davenport at The New York Times.

“This is a mandatory treaty. Governments are obligated to comply.”

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Original article posted on ScienceAlert

by PETER DOCKRILL

Scientists solve puzzle of converting gaseous carbon dioxide to fuel| ESIST

Saving the planet from climate change with a grain of sand

Converting greenhouse gas emissions into energy-rich fuel using nano silicon (Si) in a carbon-neutral carbon-cycle is illustrated.

Credit: Chenxi Qian

Every year, humans advance climate change and global warming — and quite likely our own eventual extinction — by injecting about 30 billion tonnes of carbon dioxide into the atmosphere.

A team of scientists from the University of Toronto (U of T) believes they’ve found a way to convert all these emissions into energy-rich fuel in a carbon-neutral cycle that uses a very abundant natural resource: silicon. Silicon, readily available in sand, is the seventh most-abundant element in the universe and the second most-abundant element in the earth’s crust.

The idea of converting carbon dioxide emissions to energy isn’t new: there’s been a global race to discover a material that can efficiently convert sunlight, carbon dioxide and water or hydrogen to fuel for decades. However, the chemical stability of carbon dioxide has made it difficult to find a practical solution.

“A chemistry solution to climate change requires a material that is a highly active and selective catalyst to enable the conversion of carbon dioxide to fuel. It also needs to be made of elements that are low cost, non-toxic and readily available,” said Geoffrey Ozin, a chemistry professor in U of T’s Faculty of Arts & Science, the Canada Research Chair in Materials Chemistry and lead of U of T’s Solar Fuels Research Cluster.

In an article in Nature Communications published August 23, Ozin and colleagues report silicon nanocrystals that meet all the criteria. The hydride-terminated silicon nanocrystals — nanostructured hydrides for short — have an average diameter of 3.5 nanometres and feature a surface area and optical absorption strength sufficient to efficiently harvest the near-infrared, visible and ultraviolet wavelengths of light from the sun together with a powerful chemical-reducing agent on the surface that efficiently and selectively converts gaseous carbon dioxide to gaseous carbon monoxide.

The potential result: energy without harmful emissions.

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Source:University of Toronto

 

Source: Scientists solve puzzle of converting gaseous carbon dioxide to fuel: Saving the planet from climate change with a grain of sand — ScienceDaily

Scientists convert carbon dioxide, create electricity | ESIST

This graphic explains novel method for capturing the greenhouse gas and converting it to a useful product — while producing electrical energy.

Credit: Cornell University

While the human race will always leave its carbon footprint on the Earth, it must continue to find ways to lessen the impact of its fossil fuel consumption.

“Carbon capture” technologies — chemically trapping carbon dioxide before it is released into the atmosphere — is one approach. In a recent study, Cornell University researchers disclose a novel method for capturing the greenhouse gas and converting it to a useful product — while producing electrical energy.

Lynden Archer, the James A. Friend Family Distinguished Professor of Engineering, and doctoral student Wajdi Al Sadat have developed an oxygen-assisted aluminum/carbon dioxide power cell that uses electrochemical reactions to both sequester the carbon dioxide and produce electricity.

Their paper, “The O₂-assisted Al/CO₂ electrochemical cell: A system for CO₂capture/conversion and electric power generation,” was published July 20 inScience Advances.

The group’s proposed cell would use aluminum as the anode and mixed streams of carbon dioxide and oxygen as the active ingredients of the cathode. The electrochemical reactions between the anode and the cathode would sequester the carbon dioxide into carbon-rich compounds while also producing electricity and a valuable oxalate as a byproduct.

In most current carbon-capture models, the carbon is captured in fluids or solids, which are then heated or depressurized to release the carbon dioxide. The concentrated gas must then be compressed and transported to industries able to reuse it, or sequestered underground. The findings in the study represent a possible paradigm shift, Archer said.

“The fact that we’ve designed a carbon capture technology that also generates electricity is, in and of itself, important,” he said. “One of the roadblocks to adopting current carbon dioxide capture technology in electric power plants is that the regeneration of the fluids used for capturing carbon dioxide utilize as much as 25 percent of the energy output of the plant. This seriously limits commercial viability of such technology. Additionally, the captured carbon dioxide must be transported to sites where it can be sequestered or reused, which requires new infrastructure.”

The group reported that their electrochemical cell generated 13 ampere hours per gram of porous carbon (as the cathode) at a discharge potential of around 1.4 volts. The energy produced by the cell is comparable to that produced by the highest energy-density battery systems.

Another key aspect of their findings, Archer says, is in the generation of superoxide intermediates, which are formed when the dioxide is reduced at the cathode. The superoxide reacts with the normally inert carbon dioxide, forming a carbon-carbon oxalate that is widely used in many industries, including pharmaceutical, fiber and metal smelting.

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via Cornell University

 

Source: Scientists convert carbon dioxide, create electricity — ScienceDaily