By Nancy W. Stauffer, MIT Energy Effort
September 17, 2022
Ariel Furst is the Raymond (1921) and Helen St. Laurent Career Development Professor of Chemical Engineering at MIT. Two years earlier, she chose to try utilizing something various– a material that gets more attention in conversations of biology than chemical engineering. Already, arises from work in her lab show that her uncommon method is paying off.
Professor Ariel Furst (center), undergraduate Rachel Ahlmark (left), postdoc Gang Fan (right), and their colleagues are employing biological products, including DNA, to accomplish the conversion of carbon dioxide to valuable items. Credit: Gretchen Ertl
The stumbling block
CO2 must be chemically transformed into carbon monoxide (CO) before being transformed into a helpful item. Electrochemistry, a procedure in which input voltage supplies the extra energy required to make the stable CO2 molecules respond, can promote that conversion.
To check out opportunities for improving this procedure, Furst and her research study group concentrated on the electrocatalyst, a material that improves the rate of a chain reaction without being consumed while doing so. The catalyst is essential to effective operation. Inside an electrochemical gadget, the catalyst is often suspended in an aqueous (water-based) solution. When an electric capacity (essentially a voltage) is applied to an immersed electrode, dissolved CO2 will– assisted by the driver– be converted to CO
. But theres one stumbling block: The catalyst and the CO2 must fulfill on the surface area of the electrode for the response to occur. In some studies, the catalyst is dispersed in the service, but that technique needs more catalyst and isnt very effective, according to Furst. “You have to both wait for the diffusion of CO2 to the catalyst and for the driver to reach the electrode before the reaction can happen,” she discusses. As a result, scientists worldwide have been checking out various techniques of “immobilizing” the driver on the electrode
Linking the electrode and the driver.
Prior to Furst might explore that difficulty, she needed to choose which of the 2 types of CO2 conversion catalysts to work with: the traditional solid-state catalyst or a catalyst made up of small particles. In taking a look at the literature, she concluded that small-molecule catalysts held the most assure. While their conversion performance tends to be lower than that of solid-state versions, molecular catalysts offer one crucial advantage: They can be tuned to emphasize reactions and items of interest.
2 methods are typically utilized to immobilize small-molecule catalysts on an electrode. One involves linking the driver to the electrode by strong covalent bonds– a kind of bond in which atoms share electrons; the result is a strong, basically irreversible connection. The other sets up a non-covalent attachment in between the driver and the electrode; unlike a covalent bond, this connection can quickly be broken.
Neither method is ideal. In the former case, the catalyst and electrode are securely connected, ensuring effective responses; but when the activity of the catalyst breaks down over time (which it will), the electrode can no longer be accessed. In the latter case, an abject catalyst can be eliminated; however the precise placement of the small molecules of the driver on the electrode cant be controlled, leading to an inconsistent, typically decreasing, catalytic effectiveness– and simply increasing the amount of catalyst on the electrode surface without concern for where the particles are positioned does not resolve the problem.
What was needed was a way to position the small-molecule catalyst strongly and properly on the electrode and then launch it when it degrades. For that job, Furst turned to what she and her group regard as a type of “programmable molecular Velcro”: deoxyribonucleic acid, or DNA.
Including DNA to the mix
Reference DNA to the majority of people, and they think of biological functions in living things. The members of Fursts lab view DNA as more than simply hereditary code. “DNA has these actually cool physical properties as a biomaterial that individuals do not often consider,” she states. “DNA can be used as a molecular Velcro that can stick things together with very high accuracy.”
Furst knew that DNA sequences had actually formerly been used to debilitate molecules on surfaces for other functions. So she designed a plan to use DNA to direct the immobilization of drivers for CO2 conversion.
Her method depends upon a well-understood behavior of DNA called hybridization. The familiar DNA structure is a double helix that forms when two complementary hairs link. When the series of bases (the four foundation of DNA) in the individual strands compare, hydrogen bonds form in between complementary bases, strongly connecting the strands together.
They attach a complementary hair to the driver that is floating in the liquid solution. As an outcome, the driver is firmly attached to the electrode by ways of 2 interlocked, self-assembled DNA strands, one connected to the electrode and the other to the driver.
“The connection is steady, however if we warm it up, we can get rid of the secondary strand that has the catalyst on it,” states Furst. That enables us to recycle our electrode surface areas– without having to take apart the device or do any harsh chemical steps.”
Experimental examination
To check out that concept, Furst and her group– postdocs Gang Fan and Thomas Gill, previous graduate student Nathan Corbin PhD 21, and previous postdoc Amruta Karbelkar– carried out a series of experiments utilizing 3 small-molecule drivers based on porphyrins, a group of compounds that are biologically crucial for processes ranging from enzyme activity to oxygen transport. The 3rd driver is hemin, a natural porphyrin compound used to deal with porphyria, a set of conditions that can impact the nervous system.
In their experiments, the investigators initially required to customize single strands of DNA and deposit them on among the electrodes immersed in the solution inside their electrochemical cell. Though this sounds simple, it did need some brand-new chemistry. Led by Karbelkar and third-year undergraduate researcher Rachel Ahlmark, the team established a fast, simple way to connect DNA to electrodes. For this work, the scientists focus was on connecting DNA, however the “tethering” chemistry they developed can likewise be used to connect enzymes (protein drivers), and Furst thinks it will be extremely beneficial as a general technique for modifying carbon electrodes.
When the single strands of DNA were transferred on the electrode, the scientists synthesized complementary hairs and attached to them among the 3 drivers. When the DNA hairs with the driver were included to the service in the electrochemical cell, they readily hybridized with the DNA strands on the electrode. After half-an-hour, the scientists used a voltage to the electrode to chemically convert CO2 liquified in the option and used a gas chromatograph to analyze the makeup of the gases produced by the conversion.
The group found that when the DNA-linked drivers were easily dispersed in the service, they were highly soluble– even when they included small-molecule catalysts that dont dissolve in water by themselves. Undoubtedly, while porphyrin-based catalysts in option typically stick together, as soon as the DNA hairs were attached, that disadvantageous habits was no longer evident.
“So simply connecting that single strand of DNA to the driver in service makes those catalysts more steady,” says Furst. Experimental outcomes revealed that including the DNA prevented the catalyst from degrading at voltages of interest for practical devices. With all three catalysts in service, the DNA modification substantially increased the production of CO per minute.
Permitting the DNA-linked catalyst to hybridize with the DNA linked to the electrode brought further enhancements, even compared to the very same DNA-linked catalyst in solution. For example, as a result of the DNA-directed assembly, the driver wound up strongly connected to the electrode, and the catalyst stability was further improved. In spite of being extremely soluble in liquid services, the DNA-linked driver particles stayed hybridized at the surface of the electrode, even under severe speculative conditions.
Debilitating the DNA-linked driver on the electrode likewise substantially increased the rate of CO production. In a series of experiments, the scientists kept track of the CO production rate with each of their drivers in option without attached DNA hairs– the traditional setup– and then with them incapacitated by DNA on the electrode. With all 3 drivers, the amount of CO generated per minute was far greater when the DNA-linked catalyst was incapacitated on the electrode.
Additionally, paralyzing the DNA-linked driver on the electrode considerably increased the “selectivity” in terms of the products. That tendency was eased by including DNA to the driver in solution– and even more so when the catalyst was paralyzed on the electrode using DNA. For both the cobalt-porphyrin driver and the hemin-based catalyst, the development of CO relative to hydrogen was considerably greater with the DNA-linked catalyst on the electrode than in solution.
Development and plans
Furst and her team have now shown that their DNA-based approach integrates the advantages of the conventional solid-state drivers and the more recent small-molecule ones. In their experiments, they attained the highly effective chemical conversion of CO2 to CO and also were able to control the mix of items formed. And they think that their method should show scalable: DNA is commonly offered and affordable, and the amount of catalyst needed is a number of orders of magnitude lower when its immobilized using DNA.
Based on her work so far, Furst assumes that the structure and spacing of the little molecules on the electrode may straight affect both catalytic effectiveness and item selectivity. Utilizing DNA to manage the precise positioning of her small-molecule catalysts, she plans to examine those effects and after that extrapolate design criteria that can be used to other classes of energy-conversion catalysts. Ultimately, she hopes to establish a predictive algorithm that researchers can use as they create electrocatalytic systems for a wide variety of applications.
Reference: “DNA-based immobilization for improved electrochemical carbon dioxide reduction” by Gang Fan, Nathan Corbin, Thomas Gill, Amruta Karbelkar and Ariel Furst, 19 May 2022, ChemRxiv.DOI: 10.26434/ chemrxiv-2022-qll2k.
This research was supported by a grant from the MIT Energy Initiative Seed Fund.
Prior to Furst might dive into that obstacle, she needed to choose which of the two types of CO2 conversion drivers to work with: the conventional solid-state driver or a catalyst made up of little molecules. In the latter case, an abject driver can be gotten rid of; however the precise positioning of the little molecules of the driver on the electrode cant be managed, leading to an inconsistent, frequently reducing, catalytic effectiveness– and simply increasing the amount of catalyst on the electrode surface area without concern for where the particles are positioned does not solve the issue.
As an outcome, the driver is firmly affixed to the electrode by means of 2 interlocked, self-assembled DNA hairs, one connected to the electrode and the other to the driver.
That tendency was reduced by including DNA to the driver in option– and even more so when the catalyst was incapacitated on the electrode using DNA. For both the cobalt-porphyrin driver and the hemin-based catalyst, the formation of CO relative to hydrogen was considerably greater with the DNA-linked catalyst on the electrode than in service.
Chemical engineers at MIT are utilizing DNA to assist convert CO2 into important chemicals.
MIT Assistant Professor Ariel Furst and her associates are aiming to DNA to assist the process.
A significant goal in the energy sector has been to chemically convert released CO2 into fuels or other important chemicals. CO2 is available in abundance, it has not yet been widely utilized to produce value-added items.
Among the main reasons is that CO2 particles are extremely stable. Therefore, they are not really susceptible to being chemically converted to a various type. Scientists have actually sought products and gadget styles that could assist stimulate that conversion, but absolutely nothing has worked well enough yet to produce an effective, economical system.