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Chemical and Biomolecular Engineering

Hong Yang, a chemical engineering professor at Illinois since 2012, has been named the Richard C. Alkire Chair in Chemical Engineering in a ceremony honoring his commitment and leadership within the field.

Yang is recognized worldwide for his contribution to the fundamental understanding and processing of nanostructured materials such as precisely controlled metal, metal alloy, and oxide nanoparticles. Yang’s research places an emphasis on sustainability, with research applications in energy, and chemical conversion as applied to fuel cell and battery, generation of hydrogen, and utilization of carbon dioxide. He is one of the most cited researchers in his field.

Provost Andreas Cangellaris awarded Yang his medallion.

“Hong Yang is celebrated across the world,” Cangellaris said. “The work that professor Yang is doing is truly pioneering for the green future of our world. He has ways of making things happen that a few years ago were unthinkable.”

Professors Hong Yang and Richard Alkire

Yang graduated from Tsinghua University, Beijing, China, in 1989 with a bachelor’s degree; in 1994, he earned his master’s degree from the University of Victoria, and in 1998 he earned his doctoral degree from the University of Toronto. He joined the faculty at the University of Rochester, and in 2012 he joined the Department of Chemical and Biomolecular Engineering at Illinois.

In his early years on campus, when people asked him why he made a mid-career move to Illinois, Yang often told them it was because of the excellent engineering research and infrastructure. But he’s come to understand that many people, including himself, grow to love the university because of its community, which provides opportunities for collaboration, and which demands academic vigor as faculty are consistently challenged to bring their “A game” to everything they do, he said.

“With this endowed position, I am looking forward to working with my students and colleagues to tackle exciting green technology problems in the future,” Yang said.

The Richard Alkire Chair in Chemical and Biomolecular Engineering recognizes expertise and academic abilities within the field of chemical engineering. The predecessor of this named position was established by Charles J. (BS, ’44, chemical engineering) and Dorothy G. Prizer.

Prizer spent the majority of his professional career serving in a variety of executive roles for the Rohm & Haas Company, including corporate vice president in several divisions and ultimately retiring as vice president and regional director of corporate operations, North America region.

The present chair was also established through the generosity of former students and friends of Alkire, who joined the department in 1969. Alkire, the Charles J. and Dorothy G. Prizer Chair Emeritus, is a member of the National Academy of Engineering.

“The donors to this Chair are expressing a sense of deep gratitude that has lasted for decades. It is deeper than a high H-Factor, or an impressive Front Cover on a prestigious journal. It is to be cherished. It is a core value of a great university. These donors want to pay back for something important that happened when they were students here. It is that spirit that is embedded in this Chair,” Alkire said.

“The research of Professor Yang represents a superb example of a wonderful group of brilliant young people working on important high-impact problems such as the reduction of oxygen, one of the most important reactions of them all,” he added.

During the ceremony, Yang thanked his colleagues and LAS, as well as his wife, Xinhong, and two children, Chloe and Dan.

“Investitures bring together everything I love about the academy. Fantastic faculty, remarkable students, family, and donors,” said Matthew Ando, associate dean for life and physical sciences in the College of LAS. “Hopefully the trust placed upon you in this way will enable you to act when great ideas happen. What’s really exciting is when someone gives you the resources to pursue a great idea with a friend down the hall. That’s what these investitures do.”

Postdoctoral researcher Jaemin Kim, professor of chemical and biomolecular engineering Hong Yang and graduate student Pei-Chieh (Jack) Shih are part of a team that developed a new material that helps split water molecules for hydrogen fuel production. Photo by L. Brian Stauffer.

Breaking the bonds between oxygen and hydrogen in water could be a key to the creation of hydrogen in a sustainable manner, but finding an economically viable technique for this has proved difficult. Researchers report a new hydrogen-generating catalyst that clears many of the obstacles – abundance, stability in acid conditions and efficiency.

In the journal Angewandte Chemie, researchers from the University of Illinois at Urbana-Champaign report on an electrocatalytic material made from mixing metal compounds with substance called perchloric acid.

Electrolyzers use electricity to break water molecules into oxygen and hydrogen. The most efficient of these devices use corrosive acids and electrode materials made of the metal compounds iridium oxide or ruthenium oxide. Iridium oxide is the more stable of the two, but iridium is one of the least abundant elements on Earth, so researchers are in search of an alternative material.

“Much of the previous work was performed with electrolyzers made from just two elements – one metal and oxygen,” said Hong Yang, a co-author and professor of chemical and biomolecular engineering at Illinois. “In a recent study, we found if a compound has two metal elements – yttrium and ruthenium – and oxygen, the rate of water-splitting reaction increased.”

Yao Qin, a co-author and former member of Yang’s group, first experimented with the procedure for making this new material by using different acids and heating temperatures to increase the rate of the water-splitting reaction.

The researchers found that when they used perchloric acid as a catalyst and let the mixture react under heat, the physical nature of the yttrium ruthenate product changed.

“The material became more porous and also had a new crystalline structure, different from all the solid catalysts we made before,” said Jaemin Kim, the lead author and a postdoctoral researcher. The new porous material the team developed – a pyrochlore oxide of yttrium ruthenate – can split water molecules at a higher rate than the current industry standard.

“Because of the increased activity it promotes, a porous structure is highly desirable when it comes electrocatalysts,” Yang said. “These pores can be produced synthetically with nanometer-sized templates and substances for making ceramics; however, those can’t hold up under the high-temperature conditions needed for making high-quality solid catalysts.”

Yang and his team looked at the structure of their new material with an electron microscope and found that it is four times more porous than the original yttrium ruthenate they developed in a previous study, and three times that of the iridium and ruthenium oxides used commercially.

“It was surprising to find that the acid we chose as a catalyst for this reaction turned out to improve the structure of the material used for the electrodes,” Yang said. “This realization was fortuitous and quite valuable for us.”

The next steps for the group are to fabricate a laboratory-scale device for further testing and to continue to improve the porous electrode stability in acidic environments, Yang said.

“Stability of the electrodes in acid will always be a problem, but we feel that we have come up with something new and different when compared with other work in this area,” Yang said. “This type of research will be quite impactful regarding hydrogen generation for sustainable energy in the future.”

Graduate student Pei-Chieh Shih, Zaid Al-Bardan and Argonne National Laboratory researcher Cheng-Jun Sun also contributed to this research.acidic media” is available online and from the U. of I. News Bureau. DOI: 10.1002/anie.201808825

Dr. Jonathan Sweedler, director of the School of Chemical Sciences, has announced two new chairs in the Department of Chemical and Biomolecular Engineering.

Dr. Paul J. A. Kenis, currently the William H. and Janet G. Lycan Professor will be the Elio Eliakim Tarika Endowed Chair in Chemical Engineering. Dr. Hong Yang, the Richard C. Alkire Professor, will be the Richard C. Alkire Chair in Chemical and Biomolecular Engineering.

Both chair appointments will start in August 2018, and investitures are being planned for Fall 2018. Investiture as a named chair or professor is one of the highest honors a faculty member can receive, and the selection process requires careful and critical examination of an individual’s career.

Paul J. A. KenisElio Eliakim Tarika Endowed Chair in Chemical Engineering

Dr. Paul Kenis

The Elio Eliakim Tarika Endowed Chair in Chemical Engineering, or “Tarika Chair,” recognizes excellence in research and was created in honor of Elio Tarika by his late wife, Nancy Tarika. Elio was a native of Cairo, Egypt, who arrived in the U.S. on the first Liberty ship that sailed from Alexandria, Egypt, after World War II. He obtained his BS in Chemical Engineering from Illinois in 1949, then had a long and successful career as a researcher and executive in the chemical industry, mostly with Union Carbide. In 1990, Elio retired as chairman of the board of the Viskase Corporation.

Kenis graduated from Radboud University in Nijmegen, The Netherlands with a B.S. in Chemistry in 1993. He then earned a Ph.D. in Chemical Engineering from the University of Twente, The Netherlands in 1997. He was a Postdoctoral Fellow at Harvard University under George Whitesides from December 1997 to August 2000. He then joined the Chemical and Biomolecular Engineering faculty at the University of Illinois as an Assistant Professor, and has been a full Professor since 2010, serving as the department’s head since 2011.

His research focuses on the development of microchemical systems to study fundamental phenomena (including protein chemistry and cell biology) as well as a wide range of applications in energy conversion and chemical synthesis. Most recently his efforts have focused on microreactors for the synthesis of semiconducting nanoparticles, microfluidic approaches to study protein folding as well as protein and pharmaceutical crystallization, and, most prominently, on developing catalysts, electrodes, and electrolyzers for the efficient electrocatalytic reduction of carbon dioxide to value-added chemicals.

Hong Yang – Richard Alkire Chair in Chemical and Biomolecular Engineering

Dr. Hong Yang

The Richard Alkire Chair in Chemical and Biomolecular Engineering, or “Alkire Chair,” recognizes expertise and academic abilities within the field of chemical engineering. The predecessor of this named position was established by Charles J. and Dorothy G. Prizer. Mr. Prizer received a B.S. in Chemical Engineering from Illinois and spent the majority of his professional career serving in a variety of executive roles for the Rohm & Haas Company, including corporate vice president in several divisions and ultimately retiring as Vice President and Regional Director of Corporate Operations, North America Region. The present chair has been established in honor of Professor Alkire, in part aided by the generosity of alumni and friends of Dr. Alkire, who joined the department in 1969. Alkire, the Charles J. and Dorothy G. Prizer Chair Emeritus, is a member of the National Academy of Engineering.

Dr. Yang graduated from Tsinghua University, Beijing, China, with a B.S. in Chemistry in 1989. He earned his M.S. from the University of Victoria in 1994, and his Ph.D. from the University of Toronto in 1998. He then was a postdoctoral fellow at Harvard University under George Whitesides from September 1998 to June 2001. He joined the Chemical and Biomolecular Engineering faculty at the University of Illinois as a full professor in 2012.

His current research efforts are focused on new nanostructures (size, shape, composition and surface) that allow the change of electron band property and the surface atomic arrangement of the metal catalyst by incorporating or changing other metal elements. These synthetic capabilities allow for the chemisorption of the oxygen containing intermediates that have the largest impact on the kinetics for oxygen reduction and evolution reactions and improving the catalyst activity and stability for applications in hydrogen fuel cell, battery, and electrolyzer for hydrogen production through water splitting.

A University of Illinois research team has invented a highly-efficient method for producing precision catalysts that can be used for cathode reaction in hydrogen fuel cells for automobiles. The technique promises to increase the efficiency of producing shape-controlled catalysts that could have benefits beyond the automotive industry.

Countless chemical and petrochemical processes involve the use of a catalyst. One of the current challenges in developing hydrogen fuel cells is to produce the high-performance, low-cost catalyst at scale.

Kai-Chieh Tsao (left) and Professor Hong Yang have published their results in the journal Small.
Kai-Chieh Tsao (left) and Professor Hong Yang have published their results in the journal Small.

“The geometric shape of the catalyst is crucial to the highest possible conversion rate of fuel molecules in a hydrogen fuel cell,” said Hong Yang, Richard C. Alkire Professor in Chemical Engineering. “The atomic arrangement determines how close the molecules can get together to react. The challenge is finding the right distribution of surface atoms so that they have the molecule at the right strength. If it is too strong, the molecule won’t leave the surface. If it’s too weak, it won’t adsorb.”

In 2007, researchers proved that platinum combined with another metal (in this case nickel) could enhance the electrocatalyst performance about tenfold simply by improving the geometry.

Typically, researchers produce the catalyst by converting molecule precursors in liquid into nanoparticle catalysts. A shape of a solid-state catalyst is more predictable and consistent if they are produced in well-controlled liquid media.  That “batch system” can be quite precise to create those geometric shapes that result in high performance.  The Yang group previously used this method and worked with the automobile industry, namely General Motors, to improve the efficiency of catalysts for hydrogen fuel cells, which converts chemical energy stored in hydrogen fuel into electricity and pure water.

The batch system, however, is inefficient in production, as it takes more time and multiple processing steps to produce.  A current problem has been producing such precise catalysts at scale.

Yang and his graduate student, Kai-Chieh Tsao, have come up with a solution aimed to solve this problem. This work was published in Small, a journal of nano and micro technology.

The technique the group has developed involves a novel conveyor belt system, which produces solid-state platinum (Pt) nanocubes and its nickel alloy (Pt3Ni) nanooctahedra by using an aerosol-assisted airbrush to disperse precursors together with carbon particles as the catalyst support on a substrate and finely controlling the reaction conditions while the substance is transported through a tube with carbon monoxide as a reactive carrier gas. The powders are heated and passed through the tubular reactor, producing the solid-state catalysts. The method thus allows for a continuous production, which is scalable for large-scale production purpose.

“Carbon monoxide can interact predictably with a range of platinum group metals,” Yang said. “Those metals are very active, both in fuel cells and in other chemical industry processes. The conveyor belt transport technique mimics the existing technology for handling the fluid phase. For example, when pumping gasoline, the raw material (crude oil) is pumped continuously at the one end, producing gasoline on the other. We want to translate that principle by using a conveyor belt or solid supported catalyst synthesis in one step. The difference in our method is, in principle, we can continuously make a uniform catalyst on solid support through the conveyor belt system.”

Through transmission electron microscopy (TEM), the team demonstrated that the metal cube catalysts were produced uniformly in both size and shape on the support.

Yang reiterates that although the nanomaterial has a nice property, in order to have the kind of impact on the chemical industry, it must be able to be produced at scale. The ultimate goal for his group is to create a viable commercial product that can do just that.

“We are moving in that direction,” Yang said. “One can start to generate a uniform catalyst using our system. We have been using batch synthesis to make catalysts for fuel cells, but now we want to apply this technology to a high-production run to move to the next phase.”

Although Yang has proven the effectiveness of the technique, he and his group are increasing the efficiency by testing different geometric forms of the resulting catalysts.

“If we can demonstrate applications that show high production rates of the catalyst we generated with dramatic enhancement of performance in comparison with the others, that could be the turning point for this technology,” Yang said. “In the example of the fuel cell catalyst, the challenge is to reduce the cost of the catalyst. You can imagine if one can improve the performance (generating the same amount of power by using less catalyst), the fuel cell itself will be more efficient.”

While the technique is targeted for the hydrogen fuel cell application in the automobile industry, Yang hopes to apply that same technique to produce high-precision catalysts for other chemical conversion processes, such as creation of epoxy from hydrocarbon or conversion of carbon dioxide into commodity chemicals.

“In principle, all these solid catalysts follow the same working principle,” Yang said. “You need to have the right structure and atoms on the surface that can allow molecules quickly react and leave the surface. It has to allow the chemicals to have the right distance for the most efficient adsorption rate.”

Kai-Chieh Tsao (left) and Professor Hong Yang have published their results in Small.

By Mike Koon, Marketing and Communications Coordinator, College of Engineering.

For more information about the technology, contact Professor hy66atillinois [dot] edu (Hong Yang).

Six researchers from the University of Illinois, include Chemical and Biomolecular Engineering Professor Hong Yang, have been named Fellows of the American Association for the Advancement of Science.

Hong Yang, Richard C. Alkire Professor in Chemical Engineering
Hong Yang, Richard C. Alkire Professor in Chemical Engineering

AAAS is honoring 347 new fellows this year for their “scientifically or socially distinguished efforts to advance science or its applications.” Fellows are AAAS members selected by their peers for outstanding contributions to the field. The new fellows will be recognized at the annual AAAS meeting in February 2016.

The newly appointed AAAS fellows include: Hong Yang, the Richard C. Alkire Professor in Chemical Engineering in the department of chemical and biomolecular engineering; U. of I. President Timothy Killeen; William Metcalf, the G. William Arends Professor in Molecular and Cellular Biology in the department of microbiology; William Mischo, the Berthold Family Professor of Information Access and Discovery and the head of the Grainger Engineering Library Information Center; Ralph Nuzzo, the G.L. Clark Professor of Chemistry and a professor of materials science and engineering; and statistics professor emeritus Stephen Portnoy.

Hong Yang earned his Ph.D. from the University of Toronto in 1998 and joined the Illinois faculty in 2012. He was selected for the “discovery of a new synthesis platform for precisely controlled noble metal alloy nanostructures, with applications in electrocatalysis for fuel cells and batteries.”

Professor Yang was recently invested as the Richard C. Alkire Professor in Chemical Engineering.

Timothy Killeen, who took office in May as the university’s 20th president, earned his Ph.D. at University College London in 1975. Before coming to Illinois, he served as the vice chancellor for research and president of the Research Foundation of the State University of New York. AAAS recognized him for “distinguished contributions to optical interferometry, education and government administration, and leadership in professional service.”

William Metcalf earned his Ph.D. from Purdue University in 1991. He was selected for “pioneering discoveries on the genetics and enzymology of methanogenesis by archaea and the mechanisms for aerobic methane formation in marine surface waters.”

William Mischo earned his M.A. from the University of Wisconsin at Madison in 1974 and joined the U. of I. faculty in 1983. AAAS recognized him for “research relevant to the development of new digital library technologies.”

Ralph Nuzzo earned his Ph.D. from the Massachusetts Institute of Technology in 1980 and worked at Bell Laboratories in materials research before joining the U. of I. faculty in 1991. AAAS acknowledged him for “distinguished contributions to materials chemistry, particularly for the development of self-assembled monolayers as systems for the design of functional molecular surfaces and interfaces.”

Stephen Portnoy earned his Ph.D. from Stanford University in 1969 and joined the Illinois faculty in 1974. He was honored for “contributions to asymptotic theory and quantile processes and leadership in the development of robust regression methods.” He also was recognized for “building significant collaborations between statistical sciences and ecology.”

AAAS is the world’s largest scientific society. The organization was founded in 1848 and fellows have been elected annually since 1874.

By the University of Illinois News Bureau

As a young middle school student in Taiyuan, China, Hong Yang fell in love with chemical sciences when his teacher demonstrated the carbonization of sugar with sulfuric acid. As the black column of carbon foam emerged, he was hooked.

Dr. Jonathan Sweedler, Director, School of Chemical Sciences; Dr. Richard C. Alkire, Charles and Dorothy Prizer Chair Emeritus; Dr. Hong Yang, Richard C. Alkire Professor in Chemical Engineering; Dr. Paul Kenis, Chemical and Biomolecular Engineering Department Head.
Dr. Jonathan Sweedler, Director, School of Chemical Sciences; Dr. Richard C. Alkire, Charles and Dorothy Prizer Chair Emeritus; Dr. Hong Yang, Richard C. Alkire Professor in Chemical Engineering; Dr. Paul Kenis, Chemical and Biomolecular Engineering Department Head.

Today Professor Yang is recognized around the world for his work in the field of nanotechnology, particularly in the synthesis of nanomaterials of well-defined structure and composition. He is a leader in the synthesis of bi- and multi-metallic Pt-based nanostructures, which are being evaluated for a range of catalytic applications including fuel cells.

On Tuesday, Oct. 6, the University of Illinois celebrated the investiture of Dr. Hong Yang as the Richard C. Alkire Professor in Chemical Engineering. Investiture as a named chair or professor is one of the highest honors a faculty member can receive.

Dr. Yang’s accomplishments “help realize the land grant mission of the university, translating knowledge into action and impact on the world,” said Interim Provost Edward Feser.

Hong Yang thanked his family, wife Xinhong Liu; daughter, Chloe J. Yang; and son, Dan Z. Yang, for their support as well as his current and former students, colleagues and department leaders. Professor Yang also said he owed a great deal of his success to his grandmother, who lived with his family when he was a young boy.

“She passed on to me not only her confidence and love, but also her strong belief in the power of knowledge,” Yang said.

Professor Yang received his B.S. degree in Chemistry from Tsinghua University, and his Ph.D. degree in Chemistry from the University of Toronto. After a postdoc at Harvard University, he was on the faculty at the University of Rochester until 2011. In 2012, he joined the Department of Chemical and Biomolecular Engineering at Illinois.

“I am also very grateful to the anonymous donor whose generosity makes this professorship possible,” he said.

Given recent budget challenges on the state and federal level, such gifts have become especially critical to building a strong faculty at Illinois, Yang said.

Feng Sheng Hu, Associate Dean, College of Liberal Arts & Sciences; Professor Richard C. Alkire, Charles and Dorothy Prizer Chair Emeritus; Hong Yang, Richard C. Alkire Professor in Chemical Engineering; and Interim Provost Edward Feser.
Feng Sheng Hu, Associate Dean, College of Liberal Arts & Sciences; Professor Richard C. Alkire, Charles and Dorothy Prizer Chair Emeritus; Hong Yang, Richard C. Alkire Professor in Chemical Engineering; and Interim Provost Edward Feser.

The Richard C. Alkire Professorship was established in honor of Professor Alkire, who joined the department in 1969. Alkire, a member of the National Academy of Engineering since 1988, is the Charles and Dorothy Prizer Chair Emeritus.

“Spanning from scholarship to administration to music, you’re a great asset to our community,” Dr. Jonathan Sweedler, director of the School of Chemical Sciences, told Alkire.

In his remarks, Professor Alkire expressed gratitude for the support alumni have given the department throughout the years.

“The support they contribute today carries with it a DNA that goes back many decades, to a time when a great faculty member did something very important. Regardless of what they say in the movies, education is personal, not business,” he said.

The department’s activities today continue to be “at the edge,” Alkire said. “Research is focused on transforming a small gold-mine of scientific understanding at the atomic scale into a big gold-mine of well-engineered products that work. The educational challenge is to re-invent a curriculum that provides routine engineering methodologies for design and quality control at the molecular scale. This task will take a few decades, and is in its infancy. I can envision today’s students returning, 50 years hence, and citing words and experiences—perhaps ones that happen tomorrow morning—that inspired them to do what we think today is impossible.”

“The research of Professor Yang represents a superb example of this next-generation of engineering—the manipulation of atomic-scale distributions of elements on catalytic surfaces to optimize their catalytic activity and stability for reducing oxygen—one of the most important chemical reactions of them all,” Alkire said.

 

Professor Hong Yang, the Richard C. Alkire Professor of Chemical Engineering, Professor Jian-Min Zuo of Materials Science and Engineering, and their research groups have recently published a paper in Nano Letters on a new growth model uncovered by the novel liquid flow phase in situ transmission electron microscopy (TEM) technique.

“Such research has implications on the design of catalysts for various applications, such as fuel cells and batteries. It is the first of such study from this team at the University of Illinois and one of several exciting projects we are working on in related areas,” Professor Yang said. According to Professor Zuo, the discovery was made possible by performing the experiment under a powerful electron microscope and keeping the electron beam interference as low as possible using a low intensity beam and a sensitive electron detector.

In the article “Growth of Au on Pt Icosahedral Nanoparticles Revealed by Low-Dose In Situ TEM,” the authors explain how they used in situ TEM for quantitative study of nucleation and growth kinetics and how this tool can provide valuable new insight into the design and precise control of heterogeneous nanostructures. The accurate control of surface structure and composition down to atomic level is what will be needed for advanced catalysts that have exceptionally high activity and selectivity. The follow-up work being carried out looks at using the new techniques in the study of chemical etching, corrosion, and electrochemical reactions—all important processes in fuel cell and battery applications.

In addition to Professor Yang, the article’s authors include Dr. Jianbo Wu with the Department of Chemical and Biomolecular Engineering and Engineering and the Department of Materials Science and Engineering, Professor Jian-Min Zuo and Mr. Wenpei Gao, with the Department of Materials Science and Engineering and Frederick Seitz Materials Research Laboratory, all at the University of Illinois; Drs. Jianguo Wen and Dean Miller with the Electron Microscopy Center in the Center for Nanoscale Materials at Argonne National Laboratory; and Dr. Ping Lu with the Sandia National Laboratories.

The National Science Foundation, U.S. Department of Energy and University of Illinois supported this research.

Professor Hong Yang from the Chemical and Biomolecular Engineering Department at the University of Illinois, and Professor Yadong Yin of the University of California Riverside, are the guest editors for the October 2013 special issue of ChemSusChem.  
Cover from the October 2013 ChemSusChem journal that focuses on nanostructures for energy conversion and storage.
Cover from the October 2013 ChemSusChem journal that focuses on nanostructures for energy conversion and storage.

The cover image shows how a large variety of nanostructures can be applied to reach sustainability goals. The theme for this issue is on Nanostructures for Energy Conversion and Storage and covers articles about the shape control of nanostructures and their use.

University of Illinois researchers have developed a new way to produce highly uniform nanocrystals used for both fundamental and applied nanotechnology projects.

“We have developed a unique approach for the synthesis of highly uniform icosahedral nanoparticles made of platinum (Pt),” explained Hong Yang, a professor of chemical and biomolecular engineering and a faculty affiliate at the Center for Nanoscale Science and Technology at Illinois. “This is important both in fundamental studies—nanoscience and nanotechnology—and in applied sciences such as high performance fuel cell catalysts.
Micrograph showing the uniformity of the nanocrystals at low magnification
Micrograph showing the uniformity of the nanocrystals at low magnification

Yang’s research group focuses on the synthesis and understanding structure-property relationship of nanostructured materials for applications in energy, catalysis, and biotechnology. Its paper, “Highly Uniform Platinum Icosahedra Made by the Hot Injection-Assisted GRAILS Method,” was published this week in Nano Letters.

“Although polyhedral nanostructures, such as a cube, tetrahedron, octahedron, cuboctahedron, and even icosahedron, have been synthesized for several noble metals, uniform Pt icosahedra do not form readily and are rarely made,” stated Wei Zhou, a visiting scholar with Yang’s research group and the paper’s first author.

An icosahedron crystal is a polyhedron with 20 identical equilateral triangular faces, 30 edges and 12 vertices. According to Yang, icosahedral shaped crystals can improve the catalytic activity in oxygen reduction reaction partly because of the surface strain.

“The key reaction step to improve the activity of oxygen electrode catalysts in the hydrogen fuel cell is to optimize the bond strength between Pt and absorbed oxygen-containing intermediate species,” Yang said. “This allows the rapid production of water and let the intermediate react and leave the surface quickly so the catalyst site can be used again.”

Mode of formation for various Pt nanocrystals
Mode of formation for various Pt nanocrystals

“Unlike many other forms of metal nanoparticles, an icosahedral nanocrystal is not a single crystal, but has many twin (defect) boundaries within this shape. Previous simulation data suggest that it is unstable for Pt nanoparticles to exist in this shape at about >1-2 nm and, indeed, it is uncommon for Pt nanoparticles to have this morphology.”

Highly uniform Pt icosahedral nanocrystals with an edge length of 8.8 nm were synthesized by Yang’s research group.They were made from platinum acetylacetonate in dodecylamine and with small amount of oleic acid using a hot injection-assisted GRAILS (gas reducing agent in liquid solution) approach. In the GRAILS approach, the inclusion of CO gas greatly facilitates the formation of well-defined shapes.

“Our results showed that the key factors for the shape control include fast nucleation, kinetically controlled growth, and protection from oxidation by air,” Zhou added.

Micrograph showing array of atoms and tetrahedral subunits in a single icosahedral Pt particle
Micrograph showing array of atoms and tetrahedral subunits in a single icosahedral Pt particle.

By adjusting these key parameters, Pt hyper-branched rods, cubes, and octapods were also obtained.

“We are currently studying why this shape is formed in our systems and how we can use this principle to produce other unusual and potentially useful Pt and its alloy nanoparticles,” Yang noted. “The high purity (>95%) of the products provides the ideal model materials for studying the structure/morphology-property relationships. Such mechanistic understanding is valuable for the design of advanced, high performance metal and metal alloy catalysts.”

This work was supported by the National Science Foundation.

_______________________
Contact: Hong Yang, Department of Chemical and Biomolecular Engineering, 217/244-6730.
Writer: Rick Kubetz, Engineering Communications Office, University of Illinois at Urbana-Champaign, 217/244-7716.
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