Georgia U.S. Sen. Jon Ossoff visited Georgia Tech’s campus on Friday, April 29. His stop at Tech brought major stakeholders in Georgia together in a roundtable discussion to explore the potential for a hydrogen hub in the Southeast.

The Biden administration regards clean hydrogen as a critical component in a plan to transition the American energy infrastructure toward net-zero carbon emissions by 2050. The Bipartisan Infrastructure Law includes $8 billion to establish regional hydrogen hubs that will conduct the research and development necessary to make hydrogen a viable, cost-effective, and clean energy carrier.

Sen. Ossoff has been a vocal supporter of clean and renewable energy initiatives and spoke during the roundtable discussion on the possibilities of the state of Georgia being an early adopter in the emerging clean energy market.

Hydrogen is one of Georgia Tech’s strategic research initiatives, and the Strategic Energy Institute, led by Tech Professor Timothy Lieuwen, has been very instrumental in coordinating the energy research community, which is active in hydrogen-related research.

Ossoff said that in hosting this event at Georgia Tech, he hopes to position the state of Georgia and Georgia Tech as key players in the receipt of federal funds to help accelerate the Biden administration’s goal of using hydrogen as a clean energy carrier rather than relying on expensive technology.

“Exciting opportunities in hydrogen energy are coming to Georgia,” said Ossoff. “This is a vital energy source as we continue to reduce pollution and move toward clean energy.” 

The climate crisis requires ramping up usage of renewable energy sources like solar and wind, but with intermittent availability, scalable energy storage is a challenge.  

Hydrogen —especially carbon-free green hydrogen—has emerged as a promising clean energy carrier and storage option for renewable energy such as solar and wind. It adds no carbon emissions to the atmosphere, but currently is costly and complex to create. 

One way to produce green hydrogen is electrochemical water splitting. This process involves running electricity through water in the presence of catalysts (reaction-enhancing substances) to yield hydrogen and oxygen. 

Researchers at Georgia Institute of Technology and Georgia Tech Research Institute (GTRI) have developed a new water-splitting process and material that maximize the efficiency of producing green hydrogen, making it an affordable and accessible option for industrial partners that want to convert to green hydrogen for renewable energy storage instead of conventional, carbon-emitting hydrogen production from natural gas.

The Georgia Tech findings come as climate experts agree that hydrogen will be critical for the world’s top industrial sectors to achieve their net-zero emission goals. Last summer, the Biden Administration set a goal to reduce the cost of clean hydrogen by 80% in one decade. Dubbed the Hydrogen Shot, the Department of Energy-led initiative seeks to cut the cost of “clean” or green hydrogen to $1 per kilogram by 2030.

Scientists hope to replace natural gas and coal, currently used today for storing extra electric energy at the grid level, with green hydrogen because it doesn’t contribute to carbon emissions, making it a more environmentally friendly means for storing renewable electricity. The focus of their research is electrolysis, or the process of using electricity to split water into hydrogen and oxygen.

Less Costly, More Durable Materials

Georgia Tech’s research team hopes to make green hydrogen less costly and more durable using hybrid materials for the electrocatalyst. Today, the process relies on expensive noble metal components such as platinum and iridium, the preferred catalysts for producing hydrogen through electrolysis at scale. These elements are expensive and rare, which has stalled the move to replace gas for hydrogen-based power. In fact,  green hydrogen accounted for less than 1% of annual hydrogen production in 2020, in large part because of this expense, according to market research firm Wood Mackenzie. 

“Our work will decrease the use of those noble metals, increasing its activity as well as utilization options,” said study principal investigator Seung Woo Lee, associate professor in the George W. Woodruff School of  Mechanical Engineering, and an expert on electrochemical energy storage and conversion systems.  

In research published in the journals Applied Catalysis B: Environmental and Energy & Environmental Science, Lee and his team highlighted the interactions between metal nanoparticles and metal oxide to support design of high-performance hybrid catalysts.  

“We designed a new class of catalyst where we came up with a better oxide substrate that uses less of the noble elements,” said Lee. “These hybrid catalysts showed superior performance for both oxygen and hydrogen (splitting).”

Nanometer-scale Analysis

Their work relied upon computation and modeling from research partner, the Korea Institute of Energy Research, and X-ray measurement from Kyungpook National University and Oregon State University, which leveraged the country’s synchrotron, a football-field-sized super x-ray.   

“Using the X-ray, we can monitor the structural changes in the catalyst during the water-splitting process, at the nanometer scale,” explained Lee. “We can investigate their oxidation state or atomic configurations under operating conditions.”

Jinho Park, a research scientist at GTRI and a leading investigator of the research, said this research could help lower the barrier of equipment cost used in green hydrogen production. Besides developing hybrid catalysts, the researchers have finetuned the ability to control the catalysts’ shape as well as the interaction of metals. Key priorities were reducing the use of the catalyst in the system and at the same time, increasing its durability since the catalyst accounts for a major part of the equipment cost.

“We want to use this catalyst for a long time without degrading its performance,” he said. “Our research is not only focused on making the new catalyst, but also on understanding the reaction mechanics behind it. We believe that our efforts will help support fundamental understanding of the water splitting reaction on the catalysts and will provide significant insights to other researchers in this field,” Park said.

Catalyst Shape Matters

A key finding, according to Park, was the role of the catalyst’s shape in producing hydrogen.  “The surface structure of the catalyst is very important to determine if it’s optimized for the hydrogen production. That's why we try to control the shape of the catalyst as well as the interaction between the metals and the substrate material,” he said.

Park said some of the key applications positioned to benefit first include hydrogen stations for fuel cell electric vehicles, which today only operate in the state of California, and microgrids, a new community approach to designing and operating electric grids that rely on renewable-driven backup power.

While research is well underway to XYZ, the team is currently working with partners to explore new materials for efficient hydrogen production using artificial intelligence (AI).  

***

CITATIONS: M. Kim, J. Park, et. al, “Role of surface steps in activation of surface oxygen sites on Ir nanocrystals for oxygen evolution reaction in acidic media,” (Applied Catalysis B: Environmental, 2021) https://doi.org/10.1039/d0ee02935a

M. Kim, B. Hyun-Kim, S. Woo Lee, et. al, “Understanding synergistic metal–oxide interactions of in situ exsolved metal nanoparticles on a pyrochlore oxide support for enhanced water splitting,” (Energy Environ. Sci, 2021) Abstract

The Georgia Institute of Technology, or Georgia Tech, is a top 10 public research university developing leaders who advance technology and improve the human condition. The Institute offers business, computing, design, engineering, liberal arts, and sciences degrees. Its nearly 44,000 students representing 50 states and 149 countries, study at the main campus in Atlanta, at campuses in France and China, and through distance and online learning. As a leading technological university, Georgia Tech is an engine of economic development for Georgia, the Southeast, and the nation, conducting more than $1 billion in research annually for government, industry, and society.

A new low-temperature, multi-phase process for upgrading lignin bio-oil to hydrocarbons could help expand use of the lignin, which is now largely a waste product left over from the production of cellulose and bioethanol from trees and other woody plants.

Using a dual catalyst system of superacid and platinum particles, researchers at the Georgia Institute of Technology have shown they can add hydrogen and remove oxygen from lignin bio-oil, making the oil more useful as a fuel and source of chemical feedstocks. The process, based on an unusual hydrogen cycle, can be done at low temperature and ambient pressure, improving the practicality of the upgrade and reducing the energy input needed.

“From an environmental and sustainability standpoint, people want to use oil produced from biomass,” said Yulin Deng, a professor in Georgia Tech’s School of Chemical and Biomolecular Engineering and the Renewable Bioproducts Institute. “The worldwide lignin production from paper and bioethanol manufacturing is 50 million tons annually, and more than 95% of that is simply burned to generate heat. My lab is looking for practical methods to upgrade low molecular weight lignin compounds to make them commercially viable as high-quality biofuel and biochemicals.”

The process was described September 7 in the journal Nature Energy. The research was supported by the Renewable Bioproducts Institute at Georgia Tech. 

Cellulose, hemicelluloses, and lignin are extracted from trees, grasses, and other biomass materials. The cellulose is used to make paper, ethanol, and other products, but the lignin — a complex material that gives strength to the plants — is largely unused because it’s difficult to break down into low-viscosity oils that could serve as the starting point for kerosene or diesel fuel.

Pyrolysis techniques done at temperatures over 400 degrees Celsius can be used to create bio-oils such as phenols from the lignin, but the oils lack sufficient hydrogen and contain too many oxygen atoms to be useful as fuels. The current approach to addressing that challenge involves adding hydrogen and removing oxygen through a catalytic process known as hydrodeoxygenation. But that process now requires high temperatures and pressures 10 times higher than ambient, and it produces char and tar that quickly reduce the efficiency of the platinum catalyst.

Deng and colleagues set out to develop a new solution-based process that would add hydrogen and remove the oxygen from the oil monomers using a hydrogen buffer catalytic system. Because hydrogen has very limited solubility in water, the hydrogenation or hydrodeoxygenation reaction of lignin biofuel in solution is very difficult. Deng’s group used polyoxometalate acid (SiW₁₂) as both a hydrogen transfer agent and reaction catalyst, which helps transfer hydrogen gas from the gas-liquid interphase into the bulk solution through a reversible hydrogen extraction. The process then released hydrogen as an active species H* at a platinum-on-carbon nanoparticle surface, which solved the key issue of low solubility of hydrogen in water at low pressure.

“On the platinum, the polyoxometalate acid captures the charge from the hydrogen to form H+, which is soluble in water, but the charges can be reversibly transferred back to H+ to form active H* inside the solution,” Deng said. As an apparent result, hydrogen gas is transferred to water phase to form active H*, which can directly react with lignin oil inside the solution.  

In the second part of the unusual hydrogen cycle, the polyoxometalate acid sets the stage for removing oxygen from the bio-oil monomers. 

“The super-acid can reduce the activation energy required for removing the oxygen, and at the same time, you have more active hydrogen H* in the solution, which reacts on the molecules of oil,” Deng said. “In the solution there is a quick reaction with active hydrogen atom H* and lignin oil on the surface of the catalyst. The reversible reaction of hydrogen with polyoxometalate to form H+ and then to hydrogen atom H* on the platinum catalyst surface is a unique reversible cycle.”

The platinum particles and polyoxometalate acid can be reused for multiple cycles without reducing efficiency. The researchers also found that the efficiency of hydrogenation and hydrodeoxygenation of lignin oil varied depending on the specific monomers in the oil.

“We tested 15 or 20 different molecules that were produced by pyrolysis and found that the conversion efficiency ranged from 50% on the lower end to 99% on the higher end,” Deng said. “We did not compare the energy input cost, but the conversion efficiency was at least 10 times better than what has been reported under similar low temperature, low hydrogen pressure conditions.”  

Operating at lower temperatures — below 100 degrees Celsius — reduced the problem of char and tar formation on the platinum catalyst. Deng and his colleagues found that they could use the same platinum at least 10 times without deterioration of the catalytic activity.

Among the challenges ahead are improving the product selectivity by using different metal catalyst systems, and developing new techniques for separation and purification of the different lignin biochemicals in the solution. Platinum is expensive and in high demand for other applications, so finding a lower-cost catalyst could boost the overall practicality of the process — and perhaps make it more selective.

While helping meet the demand for bio-based oils, the new technique could also benefit the forest products, paper, and bioethanol industries by providing a potential revenue stream for lignin, which is often just burned to produce heat.

“The global lignin market size was estimated at $954.5 million in 2019, which is only a very small portion of the lignin that is produced globally. Clearly, the industry wants to find more applications for it by converting the lignin to chemicals or bio-oils,” Deng said. “There would also be an environmental benefit from using this material in better ways.” 

Beyond upgrading lignin biofuel, a broad impact of the research in Yulin's group is developing a technology to significantly increase the solubility of active hydrogen atoms or hydrogen gas in a solution, which can also be used in broader chemical reactions such as ammonia synthesis and general hydrogenation of different substances.  

In addition to Deng and first author Wei Liu, the research team also included Wenqin You, Wei Sun, Weisheng Yang, Akshay Korde, and Yutao Gong, all from Georgia Tech.

CITATION: Wei Liu, et al., “Ambient-pressure and low-temperature upgrading of lignin bio-oil to hydrocarbons using a hydrogen buffer catalytic system.” (Nature Energy, 2020).  https://doi.org/10.1038/s41560-020-00680-x

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Powering clean, efficient cars is just one way fuel cell technology could accelerate humanity into a sustainable energy future, but unfortunately, the technology has been a bit sluggish. Now, engineers may be able to essentially turbocharge fuel cells with a new catalyst.

The sluggishness comes from a chemical bottleneck, the rate of processing oxygen, a key ingredient that helps fuel cells, which are related to batteries, produce electricity. The new catalyst, a nanotechnology material developed by engineers at the Georgia Institute of Technology, markedly speeds up oxygen processing and is the subject of a new study.

Partly to accommodate oxygen’s limitations, fuel cells usually require pure hydrogen fuel, which reacts with the oxygen taken in from the air, but the costs of producing the hydrogen have been prohibitive. The new catalyst is a potential game-changer.

“It can easily convert chemical fuel into electricity with high efficiency,” said Meilin Liu, who led the study and is a Regents’ Professor in Georgia Tech’s School of Material Science and Engineering.  “It can let you use readily available fuels like methane or natural gas or just use hydrogen fuel much more efficiently,” Liu said.

Catalyst 8 times as fast

The catalyst achieves the efficiency by rushing oxygen through a fuel cell’s system. “It’s more than eight times as fast as state-of-the-art materials doing the same thing now,” said Yu Chen, a postdoctoral research associate in Liu’s lab and the study’s first author.

There are a few types of fuel cells, but the researchers worked to improve solid oxide fuel cells, which are found in some prototypical fuel cell cars. The research insights could also aid in honing supercapacitors and technology paired with solar panels, thus advancing sustainable energy beyond the new catalyst’s immediate potential to improve upon fuel cells.

Liu and Chen published their study in the March issue of the journal Joule. Their research was funded by the U.S. Department of Energy and by the Guangdong Innovative and Entrepreneurial Research Program. The fuel cell work from Liu’s lab has already attracted significant energy industry and automotive industry interest.

Naturally sluggish oxygen

Though they work differently from fuel cells and are much less efficient and clean, combustion engines make a useful metaphor to aid in understanding how fuel cells and the new catalyst work.

In a combustion engine, fuel from a tank and oxygen from the air come together to react in an explosion, producing energy that turns a crankshaft. Adding a turbocharger speeds the process up by mixing fuel and oxygen together more quickly and rushing them to combustion.

Currently, in fuel cells, hydrogen fuel from a tank and oxygen from the air also drive a process that produces energy, in this case, electricity. The two ingredients do come together in a reaction, but one very different from combustion, and much cleaner.

One end of the fuel cell, the anode, removes electrons from the hydrogen atoms in what’s called oxidation and sends the electrons through an external circuit as electric current to the cathode on the other side. There, oxygen, which is notoriously electron hungry, sucks the electrons up in what’s called reduction, and that keeps the electricity flowing.

The hydrogen, now positively charged, and the oxygen, now negatively charged, meet up to form water, which is the fuel cell’s exhaust.

In that reaction chain, oxygen is the slow link in two ways: Oxygen’s reduction takes longer than hydrogen’s oxidation, and the reduced oxygen moves more slowly through the system to meet with hydrogen. Analogous to the turbocharger, the new catalyst pushes the oxygen forward.

Oxygen rush nanotech

The catalyst is applied as a sheer coating only about two dozen nanometers thick and is comprised of two connected nanotechnology solutions that break both oxygen bottlenecks.

First, nanoparticles highly attractive to oxygen grab the O₂ molecule and let inflowing electrons quickly jump onto it, easily reducing it and tearing it into two separate oxygen ions (each one an O^2-). Then a series of chemical gaps called oxygen vacancies that are built into the nanoparticles’ structures suck up the oxygen ions like chains of vacuum cleaners passing the ions hand to hand to the second phase of the catalyst.

The second phase is a coating that is full of oxygen vacancies that can pass the O^2- even more rapidly toward its final destination.

“The oxygen goes down quickly through the channels and enters the fuel cell, where it meets with the ionized hydrogen or another electron donor like methane or natural gas.”

The ions meet to make water, which exits the fuel cell. In the case of methane fuel, pure CO₂ is also emitted, which can be captured and recycled back into fuel.

Interesting rare metals

In the first stage, there are two different flavors of nanoparticle at work. Both have cobalt, but one contains barium and the other praseodymium, a rare-earth metal that can be pricey in high quantities.

“Praseodymium is in such very small amounts that it doesn’t impact costs,” Liu said. “And the catalyst saves lots of money on fuel and on other things.”

High operating temperatures in existing fuel cells require expensive protective casings and cooling materials. The researchers believe the catalyst could help lower the temperatures by reducing electrical resistance inherent in current fuel cell chemistry. That could, in turn, reduce overall material costs.

Protective cathode coating

The second stage of the catalyst is a lattice that contains praseodymium and barium, as well as calcium and cobalt (PBCC). In addition to its catalytic function, the PBCC coating protects the cathode from degradation that can limit the lifetime of fuel cells and similar devices.

The underlying original cathode material, which contains the metals lanthanum, strontium, cobalt, and iron (LSCF), has become an industry standard but comes with a caveat.

“It’s very conductive, very good, but the problem is that strontium undergoes a diminishment called segregation in the material,” Liu said. “One component of our catalyst, PBCC, acts as a coating and keeps the LSCF a lot more stable.”

LSCF manufacturing is already well-established, and adding the catalyst coating to production could be likely reasonably achieved. Liu also is considering replacing the LSCF cathode completely with the new catalyst material, and his lab is developing a yet another catalyst to boost fuel oxidation reactions at the fuel cell’s anode.

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Also READ: Nanogenerators boost mass spectrometry. 

Coauthors of the study were: Seonyoung Yoo, Yong Ding, Ruiqiang Yan, Kai Pei, Chong Qu, Lei Zhang, Ikwhang Cha, Bote Zhao, Ben deGlee, and Ryan Murphy of Georgia Tech; YongMan Choi from the SABIC Technology Center in Saudi Arabia; Yanxiang Zhang from the Harbin Institute of Technology in China; Huijun Chen, Yan Chen, Chenghao Yang and Jiang Liu from the South China University of Technology. The research was funded by the U.S. Department of Energy SECA Core Technology Program (grants FC FE0026106 and DE-FE0031201) and the Guangdong Innovative and Entrepreneurial Research Team Program (grant 2014ZT05N200). Any opinions or findings are those of the authors and not necessarily of the funding agencies.