Physical Science and Engineering | Physical Science & Engineering

Wednesday, March 24, 2021

Congratulations Professor Bakr!

Professor Osman M. Bakr is named a Fellow of the Institute of Materials, Minerals and Mining (FIMM).

Share this

KAUST Professor of Material Science and Engineering and member of the KAUST Catalysis Center, Osman M. Bakr, has been named a Fellow of the Institute of Materials, Minerals and Mining (FIMM).

The Institute of Materials, Minerals and Mining (IOM3) is the United Kingdom’s professional body for materials and its members come from all levels within the industry and academia. The designation Fellow of the Institute of Materials, Minerals and Mining (FIMM) is the most prestigious grade of this Institute. It recognizes those who have made a significant contribution or established a record of achievement in the materials, minerals, mining fields, or other disciplines within the technical outreach of IOM3.

Research

Professor Bakr's research interests are concerned with the physics and chemistry of hybrid materials. His group works on the design and self-assembly of hybrid and inorganic materials to generate breakthrough applications in optoelectronic devices and renewable energy.

Wednesday, March 17, 2021

The right ring count to harness waste heat

Rational molecular design produces air-stable polymer-based semiconductors to better exploit waste heat for electricity.

Share this

Electronic organic materials offer promise to support alternative and green energy sources to meet escalating global energy demands and strict environmental regulations. A KAUST-led team has now developed electron-transporting, so-called n-type, organic semiconductors that could help generate electricity from waste heat released by industrial processes and homes.

Thermoelectric generators that can convert temperature changes or gradients into electricity are highly suited for harnessing waste heat. These readily scalable devices are environmentally friendly and do not have any moving parts, which makes them resistant to wear. Their efficiency in energy conversion hinges on minimizing the thermal conductivity of their components while maximizing their electrical conductivity and Seebeck coefficient, a direct measure of their ability to produce a thermoelectric current.

At the heart of thermoelectric generators are two electronically different materials, an n-type semiconductor and a hole-transporting (or p-type) semiconductor, which are joined at their ends to form a circuit. Therefore, the conversion efficiency of the generators depends on both types of semiconductor delivering optimal performance.

Organic thermoelectric materials have recently emerged as easier to process and less toxic than their cheaper and more abundant conventional inorganic counterparts. These new materials also present lower thermal conductivity, but their thermoelectric performance remains inadequate. Typically, doped n-type organic semiconductors are not stable in ambient conditions and display lower electrical conductivities than their p-type equivalents, which have been widely investigated.

“One important challenge is to find n-type organic materials with comparable performance to the best p-type semiconductors,” says research scientist, Hu Chen, who led the study within the research group of Iain McCulloch.

The KAUST team devised a systematic approach to synthesize air-stable doped n-type organic semiconductors with high thermoelectric performance. The monomers comprised cyclic amides, or lactams, fused with naphthalene and anthracene cores, generating rigid conjugated polymers by a nontoxic metal-free acid-catalyzed polymerization. “There is no rotational freedom along the backbone, which reduces energetic disorder and subsequently enhances electrical conductivity,” McCulloch says.

In this design, the electron withdrawing lactam groups produced a highly electron-deficient backbone, stabilizing the polymer under ambient conditions. Additionally, smaller cores led to larger electron affinity and, consequently, better thermoelectric performance in the polymers, “which had not been so strikingly demonstrated before this work,” McCulloch says. Chen explains that larger cores have a lower density of electron withdrawing groups, which cumulatively decrease the electron affinity.

These air-stable polymers have good commercial potential. The team is now planning to develop scalable processes to allow these materials to be integrated into thermoelectric generators.

- KAUST Discovery

Sunday, March 14, 2021

Self-stacking nanocubes

Nanoclusters with a copper-hydrogen core provide new structure-activity insights.

Share this

Copper nanomaterials with a cubic shape so perfect that they form neatly aligned stacks when brought together have been created by researchers at KAUST. The cuboid copper nanoclusters, developed by rational design, are a new member of an exotic nanomaterial family that has shown many promising properties but has remained very hard to make.

“Copper nanomaterials are a class of materials that exhibit useful properties for the fields of photoluminescence and catalysis,” says Ren-Wu Huang, a postdoc in Osman Bakr's lab, who led the research. There is great interest in synthesizing new copper nanomaterials to understand how their structure influences their function.

Copper nanoclusters, which are of an atomically precise structure, are among the few copper nanomaterials that can provide such insights at the atomic level because their total structure can be determined by single-crystal x-ray diffraction. “However, the synthesis of copper nanoclusters is still a great challenge and its pace of development is slow compared to nanoclusters made from its sister metals, silver and gold,” Huang adds.

In their latest work, the team aimed to make a hydrogen-rich polyhydrido copper nanocluster (PCN). “To create the cuboid-shaped nanoclusters, we added triphenylphosphine (Ph3P) to our synthesis reaction system,” says Bakr. Based on previously synthesized PCN structures, the team predicted that triphenylphosphine, with its rigid conical structure, would help to create a new nanocluster with a cuboid shape.

The dark-orange block-like crystals that the team isolated from the reaction mixture did prove to be a novel PCN structure with the predicted cuboid shape. Single-crystal x-ray diffraction showed that the heart of each nanocluster contained 23 copper atoms. Surrounding this core were eight triphenylphosphine groups, forming the eight corners of the cube.

Strikingly, each dark-orange crystal consisted of multiple cuboid nanoclusters, stacked neatly together in perfectly aligned rows and columns. “We found that the subtle synergy between the cuboid shape and the intercluster noncovalent bonding interactions, such as hydrogen bonding and van der Waals interactions, is the main driving force for the unique simple cubic self-assembly of nanoclusters,” Huang says.

Despite the team’s latest discoveries, copper nanocluster research is still in its infancy. “Crucial questions about the growth mechanism, structure evolution and structure-property relationships of clusters are yet to be addressed,” Bakr says. “We aim to shed light on those issues and to move forward with exploiting the potential of the clusters for important catalytic reactions.”

- KAUST Discovery

Thursday, March 11, 2021

Seeing both sides of light collection

Combining two light-absorbing materials and optimizing the flow of current improves the performance of solar cells.

Share this

Two types of materials are better than one when it comes to solar cells, as revealed by an international team that has tested a new combination of materials and architecture to improve solar-cell efficiency.

Silicon has long dominated as the premier material for solar cells, helped by its abundance as a raw material. However, perovskites, a class of hybrid organic-inorganic material, are a viable alternative due to their low-cost and large-scale manufacture and potentially higher performance. While still too unstable for full commercialization, they might become available to the market by 2022.

KAUST's Michele De Bastiani and Stefaan De Wolf, working with colleagues in Canada, Germany and Italy, now show that a combination of the two is the best approach. By optimizing the material composition and the architecture of a "tandem" device, the team has achieved efficiencies beyond commercial silicon solar panels.

Sunlight, of course, comes directly from the sun, but illumination also comes from light reflecting off other surfaces, known as albedo. A device architecture that collects light from the back as well as from the front can utilize this source. “Our bifacial tandems exploit both direct sunlight and the albedo to generate electricity in a more efficient way than their conventional counterparts,” explains De Bastiani.

He and the team started with a simple silicon device structure that was textured top and bottom to enhance light collection. They then used a solution-processing method to deposit a thin perovskite layer on top. A transparent back electrode allowed light in while also allowing a current to flow out. The researchers tested five perovskite materials, each with a different chemical composition, to increase the absorption of incoming light. In this way, they were able to identify the perovskite that best matched the electronic properties of the silicon.

“A restriction of the tandem configuration is the limited current through the lower of the two subcells,” says De Bastiani. “We designed our tandem with a unique feature: the perovskite subcell generates more current than the silicon counterpart by stealing light that would be otherwise absorbed by the bottom subcell.”

The team tested their bifacial devices and compared the performance to similar monofacial devices in various outdoor settings with a range of albedos, such as, for example, bright sandstone or concrete. They found that, in all conditions, the bifacial configuration outperformed the monofacial one.

“We are now investigating the stability of the perovskite while also scaling up the technology to the module level,” says De Bastiani. “For this, we are looking for industrial partners and sponsors.”

- KAUST Discovery

Tuesday, March 09, 2021

A cool chemical separation technology

A diverse category of porous materials can separate and purify key industrial chemicals at low temperatures.

Share this

Gas and liquid separation processes in the chemical industry could be made more efficient and environmentally friendly by using substances known as intrinsically porous materials (IPMs). KAUST researchers review the prospects for IPMs in the journal Accounts of Chemical Research.

Niveen Khashab and her team are currently heavily involved in IPM research. “We focus on making materials that will have an impact on the chemical and petrochemical industries in Saudi Arabia and the world,” says Niveen Khashab, the corresponding author of the review.

IPM materials can separate gases and liquids without using traditional high-temperature methods like heat-driven distillation.

“Through the review, we identified some IPMs with impressive performance,” says Gengwu Zhang, a postdoc in Niveen Khashab's team. He explains that these IPMs, like other porous materials being developed, could save 70 to 90 percent of the energy costs of existing technologies, with consequent environmental advantages.

A key advantage of IPMs over many other porous materials is their stability and ability to maintain their porous properties in the solid, liquid, gas or solution states. They can also be readily processed and modified when in solution, unlike many alternatives.

“They can be easily prepared on a large scale by using cheap starting materials,” says Zhang, “Some of them are even commercially available products.”

IPMs have diverse chemical structures, but they share the property of being permeated with pores that have sizes and chemical natures that make them suitable for separating and purifying different molecules. The structure of the pores determines which chemicals they can selectively adsorb, block or allow to pass through.

The KAUST authors reviewed the state of research into several IPMs, ranging from large individual molecules with internal pores to giant assemblies of molecules held together by weak multimolecular interactions.

The most promising IPMs identified in the review include the chemicals cyclodextrin, cucurbiturils, pillararenes, trianglamines and porous organic cages (POCs). These are all carbon-based or "organic" compounds. Cyclodextrins are ring-like carbohydrate structures produced from natural starch. The other compounds are specialized products of synthetic organic chemistry. The potential of these materials has been demonstrated by their performance in separating common industrial gases and liquid derivatives of the central industrial chemical benzene.

Khashab explains that the KAUST team are now addressing the challenge of scaling up their own work on IPMs, saying: “We have started discussions with Aramco for a pilot plan for liquid separations that should begin this year.”

- KAUST Discovery

Sunday, March 07, 2021

Pay-off when solar cells can keep their cool

Modeling shows the true cost of heat on PV system performance.

Share this

Lowering the operating temperature of solar panels by just a few degrees can dramatically increase the electricity they generate over their lifetime, KAUST researchers have shown. The hotter a panel gets, the lower its solar power conversion efficiency (PCE) and the faster it will degrade and fail. Finding ways to keep solar panels cool could significantly improve the return on investment of solar-power systems.

The long-standing focus of photovoltaics (PV) research has been to improve solar modules’ PCE and make solar power more cost-competitive than nonrenewable power generation. The higher the PCE, the better the PV system’s financial payback over its lifetime or the lower its "levelized cost of energy" (LCOE).

Other factors can skew these LCOE values. Capturing sunlight is inherently hot work. “All solar cells generate heat, which can lower the electrical output and shorten the module lifetime,” says Lujia Xu, a postdoc in Stefaan De Wolf’s team. Panels can regularly reach 60-65 degrees Celsius, but heat’s impact on LCOE rarely receives much consideration.

Now, Xu, De Wolf and their colleagues have developed a metric that directly compares the LCOE gains by reducing the module temperature with the LCOE gains for improving module efficiency. Under typical operating conditions, the same improvement in LCOE by finding a hard-won one percent gain in PCE could be achieved by lowering the module temperature by as little as 3 degrees Celsius, they showed.

The key factor was that hotter panels fail far more rapidly. “A 4 degrees Celsius decrease in module temperature would improve the module time to failure by more than 50 percent, and this improvement increases to over 100 percent with a 7 degrees Celsius reduction,” says Xu.

The team then developed a model to first predict the module temperature and subsequently find ways to lower it. The most effective approach was to locate modules in a windy environment with proper mounting to enable effective heat transfer to the surrounding environment. But they also showed they could achieve significant gains by making modifications at the module level. The EVA polymer encapsulant used to seal the module strongly absorbs heat from sunlight. “Replacing EVA with a more transparent material, or even adapting an encapsulant-free module technology, would be beneficial,” Xu says.

“Our results show that researchers should pay more attention to module temperature,” says De Wolf. “Because crystalline silicon solar-cell efficiency is approaching the practical upper limit, it is timely to consider other ways to decrease the LCOE, which might be even more significant than further marginal gains in cell efficiency.”

- KAUST Discovery

Thursday, March 04, 2021

Porous crystal guides reaction to transform CO2

Metal organic framework helps silver catalyst to turn greenhouse gas into useful chemical feedstock.

Share this

By embedding a silver catalyst inside a porous crystal, KAUST researchers have improved a chemical reaction that converts carbon dioxide (CO2) into carbon monoxide (CO), which is a useful feedstock for the chemical industry.

Carbon monoxide is a building block for producing hydrocarbon fuels, and many researchers are searching for ways to produce it from CO2, a greenhouse gas emitted by burning fossil fuels. One strategy involves using electricity and a catalyst to drive a so-called CO2 reduction reaction. But this reaction typically produces a variety of other products, including methane, methanol and ethylene. Separating these products significantly raises the cost of the process, so researchers hope to guide the reaction to generate a single product.

Osama Shekhah and Mohamed Eddaoudi, chemists at KAUST, in collaboration with Ted Sargent’s group at the University of Toronto, have now fine-tuned the CO2 reduction reaction using metal organic frameworks (MOFs). These porous crystals contain a lattice of metal-based nodes connected by carbon-based linker molecules. By altering these components, researchers can tailor the size of an MOF’s pores and its chemical properties.

The researchers created four different MOFs with the same overall lattice arrangement and grew 5-nanometer-wide nanoparticles of silver inside the pores of each MOF. Then they tested each MOF to find how its structure affected the CO2 reduction reaction. They monitored which products emerged from the process and studied how an activated form of CO — a crucial intermediate in the reaction — bound to the silver catalyst.

The most effective MOF contained zirconium-based nodes connected by molecules of 1,4-naphthalenedicarboxylic acid. Because it has smaller pores, its ability to trap CO2 outperformed its rivals.

The silver nanoparticle in this MOF also bound activated CO in a different way than the others, connecting in a “bridging mode” involving two bonds rather than one. This ensured that CO was less likely to transform into unwanted byproducts. “Controlling the type of the CO intermediate during the reaction has a big influence on the CO selectivity,” says Shekhah. Together, these effects boosted the efficiency of CO production to 94 percent, a dramatic improvement in selectivity.

The researchers hope to build on their strategy, making further tweaks to the MOF’s structure to enhance the CO2 reduction reaction. “We believe that this work paves the way for using MOFs as new supports for improving the activity and product selectivity of the CO2 reduction reaction by directly interacting with the gaseous intermediates and controlling their binding mode,” says Eddaoudi.

- KAUST Discovery

Monday, March 01, 2021

Hot electrons send CO2 back to the future

Catalyst nanoparticles trap an unprecedented range of wavelengths of light to convert carbon dioxide into methane.

Share this

Atmospheric carbon dioxide (CO2) is a major driver of global warming, but this gas could also serve as a valuable resource. Researchers at KAUST have developed an efficient catalyst that uses light energy to convert CO2 and hydrogen into methane (CH4). This counteracts the release of CO2 when methane is burned as a fuel.

Many researchers worldwide are exploring ways to convert CO2 into useful carbon-based chemicals, but their efforts have been limited by low efficiencies that restrict the potential for large-scale application.

“Our approach is based on the synergistic combination of light and heat, known as the photothermal effect,” says postdoc Diego Mateo. He explains that the heat is generated by the interaction of light with the catalyst, so the two forms of energy come from absorbed light.

Some other industrial approaches require heating from external sources to attain temperatures as high as 500 degrees Celsius. The KAUST research demonstrates that the reaction can be achieved using just the photothermal effect of daylight.

The catalyst is built from nickel nanoparticles on a layer of barium titanate. It captures the light in a way that kicks electrons into high energy states, known as “hot electrons”. These electrons then initiate the chemical reaction that sends CO2 back into methane. Under optimum conditions, the catalyst generates methane with nearly 100 percent selectivity and with impressive efficiency.

A major advantage is the wide range of the spectrum of light harnessed, including all visible wavelengths, in addition to the ultraviolet rays that many catalysts are restricted to. This is hugely significant since ultraviolet light comprises only 4 to 5 percent of the energy available in sunlight.

“We strongly believe that our strategy, in combination with other existing CO2 capture techniques, could be a sustainable way to convert this harmful greenhouse gas into valuable fuel,” says Mateo.

Any fuels made from CO2 would still release that gas when they are burned, but the CO2 could be repeatedly recycled from the atmosphere to fuel and back again, rather than being continually released by burning fossil fuels.

The researchers are also looking to widen the applications of their approach. “One strategy for our future research is to move towards producing other valuable chemicals, such as methanol,” says Jorge Gascon, who led the research team. The researchers also see potential for using light energy to power the production of chemicals that don’t contain carbon, such as ammonia (NH3).

- KAUST Discovery

Sunday, February 28, 2021

Pumping perovskites into a semiconductor platform

Fluid injection of perovskite semiconductors creates microwires to build different optoelectronic devices on a single silicon chip.

Share this

Materials called perovskites can be more readily incorporated into silicon-based semiconducting platforms by using a microfluidic pumping technology developed at KAUST.

The perovskites currently being explored for many applications in new technologies are diverse materials sharing the same crystalline structure as the natural mineral perovskite. These semiconducting materials show great promise in a variety of optoelectronic applications, such as light emitters, sensors and solar cells.

Compared to traditional semiconductors, perovskites are soft and unstable. “This makes it difficult to pattern them using standard lithography methods,” says materials scientist Iman Roqan at KAUST.

The challenge tackled by Roqan and her colleagues was to adapt microfluidic technologies to manipulate solutions carrying perovskites to create semiconducting microscale wires.

The first step in the procedure is to create the desired pattern of microchannels in a silicon wafer using a laser interference technique. The key innovation is to pump a solution containing perovskite ions into these microchannels, where the perovskite solidifies into the network of semiconductor wires.

“We are the first researchers to achieve this,” says Roqan, adding that the innovation, which has now been patented, will allow several different perovskite-based optoelectronic devices to be located on one silicon chip. For example, a single chip could embody a photodetector, transistor, light-emitting diode and a solar cell to act as the power supply.

To demonstrate the potential of the technique, the team have built a high-performance photodetector.

“Unlike other options, our fabrication method is extremely simple and cost-effective, while avoiding creating waste materials,” Roqan says. Some metals used in perovskites are toxic, so avoiding their release into the environment is a significant advantage.

There remain challenges to overcome to advance from this initial proof-of-concept stage. For example, the team is working to bring the stability of the devices up to a standard suitable for large-scale industrial applications. Roqan expects that work currently in progress to achieve this is likely to lead to further patents, while also building more complex demonstration devices.

One of the most likely areas for commercial development is in the growing field of "lab on a chip" technology. This can combine processes such as sensing, signaling, microfluid manipulation and chemical separations and combinations to miniaturize many laboratory procedures used in medicine and biology. With miniaturization comes portability, potentially taking a full testing laboratory process out of the lab and into the outside world.

- KAUST Discovery

In the Applied Physics Program Faculty and students engage in interdisciplinary research at the interface between fundamental physical concepts and cutting-edge technologies. They strive to exploit basic physical phenomena at the nanoscale to design innovative solutions in several applied physics specialties, such as optics and photonics, semiconductor devices, quantum electronics and novel materials for energy applications.

Find out More

The Chemical Engineering Program offers students the opportunity to develop real-world solutions to global challenges by performing rigorous coursework studies and cutting-edge research in areas including the development of new materials and processes for gas and liquid separations, for water desalination, catalysis, sustainable energy and nanotechnology as well as the advancement of new ideas in process design and control and reactor design.

Find out More

The Chemical Science Program provides a modern, research-oriented education in Chemistry. Making use of the outstanding facilities at KAUST, the program distinguishes itself with a clear focus on current challenges related to catalysis and materials.

Find out More

In the Earth Science and Engineering Program Faculty and their students engage in interdisciplinary research to understand and model geophysical processes due to the complex and changing nature of our planet. The curriculum provides a sound graduate-level education in geophysical sciences and their applications in two distinct specializations represented by two tracks:

• Fluid Earth Systems;
• Solid Earth Systems.

Find out More

Faculty and students in the Energy Resources and Petroleum Engineering (ErPE) program at KAUST engage in interdisciplinary research to understand and model hydro-chemo-thermo-mechanical coupled processes in the subsurface, with emphasis on multiphase and reactive fluid flow (oil, gas, brine, water and steam).

Find out More

The Material Science and Engineering Program equips students with fundamental and applied knowledge of nanomaterials and devices; energy conversion materials and devices; biomaterials; and advanced characterization techniques.

Find out More

The Mechanical Engineering Program focuses on the following broad areas of research: structures and mechanics of solids, fluid dynamics, thermal sciences, combustion, energy, and control and dynamics. Courses in the program provide a solid foundation in each area, covering subjects such as mechanical behavior of engineering materials, continuum mechanics, thermodynamics, experimental and numerical combustion, control design, dynamic analysis, modeling, and simulation.

Find out More

MORE INFORMATION

LOCATION

MORE INFORMATION

LOCATION

MORE INFORMATION

LOCATION

MORE INFORMATION

LOCATION

MORE INFORMATION

MORE INFORMATION

​​WATCH THE DIVISION VIDEO

​​GRADUATE PROGRAMS

Applied Physics

Chemical Engineering

Chemical Science

Earth Science and Engineering

Energy Resources and Petroleum Engineering

Material Science and Engineering

Mechanical Engineering

​FACULTIES AND RESEARCH

Faculty Research Group Labs

Affiliated Research Centers

WATCH THE DIVISION VIDEO

GRADUATE PROGRAMS

FACULTIES AND RESEARCH