Further advances in rechargeable batteries are essential to meet the demand for electric vehicles and energy storage. A novel two-dimensional (2D) material may be the solution to mitigating the so-called ‘shuttle effect’ in lithium-sulfur battery technology.��

As renewable energy production technologies improve and shrink, and electric vehicles become more popular, the demand for portable energy storage is increasing.

Currently, lithium-ion batteries are the standard, but energy density and cost must continually improve to achieve the levels of deployment needed for the most ambitious sustainability targets. Alkali metal-sulfur batteries, a type of lithium-ion battery, have emerged as a promising option, especially in applications requiring high energy storage capacity. However, one issue with metal-sulfur batteries is the so-called ‘shuttle effect’: metal particles called polysulphides dissolve into the battery’s electrolyte and are transported from the sulfur cathode to the metal anode. This reduces capacity and charging performance of the battery.

Finding a way to suppress the shuttle effect is crucial to metal-sulfur battery performance and lifetime. Khalifa University’s Hiba Al-Jayyousi, Master’s student, Department of Mechanical Engineering, Dr. Nirpendra Singh, and Dr. Muhammad Sajjad, both Department of Physics, and Prof. Kin Liao, Department of Aerospace Engineering investigated the use of 2D biphenylene sheet as a material to ‘anchor’ the metal particles and prevent them from shuttling. Their results were published in.

“Over the last three decades, lithium-ion rechargeable batteries have gained vast popularity due to their low self-discharge, ample energy storage, stable cycling performance, higher theoretical capacity and specific energy density, which directly affects the development of energy storage technologies,” Dr. Singh said. “Li-ion batteries are environmentally-friendly and suitable for portable electronics, as they offer much higher energy density than other rechargeable systems.”

Although lithium sulfur batteries have high theoretical capacity and energy density, the shuttle effect seriously hinders this technology’s development. The research team found that trapping lithium polysulfides on a biphenylene sheet effectively suppresses the shuttle effect and enhances the cycling stability of Li-S batteries. The biphenylene is a newly synthesized two-dimensional material, where the carbon atoms are arranged in a square, hexagonal, and octagonal rings. Compared with other reported two-dimensional materials such as graphene and phosphorene, the biphenylene sheet used by the research team exhibited higher binding energies with the polysulfides.

A suitable anchoring material should have excellent conductivity, high surface area, porous structure, and high binding energy with the polysulfides to prevent them from dissolving into electrolytes. Several 2D materials have been proposed and investigated, including and nonpolar polyaniline previously investigated by Dr. Singh.

“Our study shows that the biphenylene sheet is an excellent anchoring material for lithium-sulfur batteries for suppressing the shuttle effect because of its superior conductivity, porosity, and strong anchoring ability,” Al-Jayyousi said.

As energy consumption continues to rise, finding new materials that can make renewable energy generation and storage cleaner and more efficient will be key to meeting the world’s growing energy demands sustainably.��

Jade Sterling
Science Writer
20 May 2022

The post A Promising Anchoring Material for Lithium-sulfur Batteries appeared first on Khalifa University.

A review paper by Khalifa University and a team of international scientists advances understanding of the latest developments underway to improve the performance and cost of flexible, polymer solar cells

On the roadmap of the world’s transition to clean energy, solar power leads the way. Every day, the sun releases more energy than humanity needs to power everything on Earth, but tapping into that power remains the challenge. Photovoltaics are electronic devices that convert sunlight into electricity, and while their cost has plummeted recently due to intense interest, challenges remain.

Researchers from Khalifa University have collaborated with a team of international researchers to conduct a review of cathode buffer layers used in organic solar cells. Their review paper, which was published in, explains the advances researchers have made in recent years in materials science to improve the overall efficiency and lifetime of this type of photovoltaic.

Dr. Vinay Gupta and Dr. Shashikant Patole, both Assistant Professors in the Khalifa University Department of Physics, undertook their review in collaboration with researchers from the CSIR-National Physical Laboratory, India, Swansea University, United Kingdom, and the University of Jammu, India.

An organic solar cell is a type of photovoltaic that uses conductive organic polymers to absorb light and produce electricity from sunshine. Most organic photovoltaic cells are polymer solar cells.

Compared to silicon-based devices, polymer solar cells are lightweight, flexible, customizable on the molecular level and inexpensive to fabricate. But these advantages are balanced by their disadvantages: they offer about one third of the efficiency of other materials and experience substantial photochemical degradation.

“The high costs involved in inorganic photovoltaic materials have prevented these technologies from having a significant impact on global energy production,” Dr. Gupta said. “Organic photovoltaics like pervoskite solar cells (PSCs) and dye-sensitized solar cells (DSSCs) are being studied as potential alternatives, but they suffer from drawbacks including low power conversion efficiency and a short lifespan with real sensitivity to the environment.”

For their work, the research team focused on the cathode buffer layer (CBL), investigating architecture, materials and mechanisms of action to provide detailed insight into the opportunities for CBL improvement.

“The primary role of a CBL is to facilitate the collection of electrons at an electrode,” Dr. Patole said. “But it also performs several other tasks in making a solar cell function smoothly, including forming an electron selective and transport interlayer, blocking reverse charge carriers, and protecting the active layer from the hot metal atoms during thermal deposition of the cathode. For efficient organic solar cells, selecting an appropriate and high quality CBL is crucial.”

Per the researchers’ findings, an ideal CBL should be good at electron extraction and transport; have a suitable energy level that facilitates electron transport with high transparency and stability; and offer compactness for use in lightweight, flexible organic solar cells. One such material used is titanium oxide, a semiconducting metal oxide favored for its unique optical properties. Research has also found that adding cesium into the titanium oxide mix further improved device performance, while zinc oxide and zirconium oxide have also been studied.

“A diverse variety of organic materials, including conjugated polymers and small molecules, have also been explored as CBL in organic solar cells,” Dr. Gupta said.

“Small molecule-based layers offer advantages thanks to their well-defined molecular weight and the easy purification process. Quantum dots have also been explored because of their tunable optical and electrical properties, however, their commercial application is hindered by their sensitivity to the environment. Still, they remain interesting as an emerging class of nanomaterials with unique properties.”

The research team found that oxides and carbonates are popular as CBLs in organic solar cells, with zinc oxide one of the most widely used CBLs in high efficiency solar cells thanks to its chemical and thermal stability, favorable electronic and optical properties, and its low-cost fabrication. Metal and alkali fluorides, including calcium, barium, and lithium, are also popular as they improve performance in extracting electrons.

Additionally, organic solar cells can only harness sunlight from a narrow range of the electromagnetic spectrum, as ultraviolet and infrared photons can degrade the photoactive layer.

While CBLs can be used to resolve these issues and increase the lifetime of the devices, a CBL would need to perform dual functions, performing its duties at the cathode level and also in protecting the photoactive layer.

It is clear from the review paper that further improvements in performance are needed to allow polymer solar cells to compete with silicon cells, but efforts are being made to improve their viability in the photovoltaic market. The research offered by the team in their review paper will help researchers around the world develop these high efficiency cathode buffer layers for improved organic solar cell devices.��

Jade Sterling
Science Writer
31 March 2022

The post Engineered Cathode Buffer Layers for Highly Efficient Organic Solar Cells appeared first on Khalifa University.

Real-time monitoring of sugar molecules is crucial in diabetes treatment, but current methods are invasive and expensive. Researchers from Khalifa University collaborated with an international team to investigate holey graphene, a novel low-cost material, for glucose sensors.��

The World Health Organization estimates that over 382 million people worldwide have diabetes, a metabolic disorder affecting blood sugar levels. The underlying cause of diabetes varies by type, but each type can lead to excess sugar in the blood, which could cause serious health problems. For all patients, blood sugar monitoring plays a crucial role in treatment.

The sugar molecules adsorb onto a layer of holey graphene, which alters the electronic properties of the material. These changes can be measured and correspond to blood sugar monitoring data to check the blood sugar levels without invasive testing.

Dr. Muhammad Sajjad, Postdoctoral Fellow, and Dr. Nirpendra Singh, Assistant Professor, both in the Khalifa University Department of Physics, collaborated with Dr. Puspamitra Panigrahi, Hindustan Institute of Technology and Science, India, Dr. Deobrat Singh and Prof. Rajeev Ahuja, Uppsala University, Sweden, Dr. Tanveer Hussain, The University of Queensland, Australia, and Prof. J. Andreas Larsson, Lulea University of Technology, Sweden. They published their results in.

“Since the first invention of a biosensor for glucose detection, there has been tremendous demand for low-cost, portable, and reliable glucose sensors,” Dr. Singh said. “So far, most of the available devices are dependent on an expensive glucose oxidase enzyme-based recognition unit and require people to deal with the painful finger-pricking process.”

Continuous monitoring of glucose levels in people with diabetes is essential to managing the disease and avoiding the complications associated with poorly-managed treatment. There are two types of glucose monitoring sensors, enzymatic and non-enzymatic, currently available in the market.

Enzyme-based sensors use glucose dehydrogenase (GDH) or glucose oxidase (GOx), which interact with glucose molecules, resulting in an electrical response correlated to the concentration of glucose. However, these sensors are expensive to manufacture and are sensitive to environmental conditions. Non-enzymatic sensors allow glucose to be oxidized directly on the surface of the sensor, where the atoms at the surface act as the electrocatalysts, resulting in high stability with repeated use and cost-effective fabrication.

Different materials have been used to develop non-enzymatic sensors, and although each material has its own advantages and limitations, the research team focused on graphene—specifically, holey graphene.

Graphene is a unique material comprising densely packed carbon atoms arranged in a hexagonal honeycomb lattice and can be exfoliated from the graphite. It is extremely versatile and has potential applications in various fields, particularly thanks to its superior optical, electrical, thermal, and mechanical properties.

In its purest form, graphene offers myriad applications. However, in recent years, the nanoscale perforation of 2D materials has emerged as an effective strategy to enhance and widen the applications of the material beyond its pristine form.

Holey graphene is a form of graphene with nanopores in its plane. The performance of the material is affected by the pore size, density, shape, and volume. Uniform pore shape and size distribution are usually optimal as it leads to enhanced thermal, mechanical and electrical properties. These pores are perfect for adsorption, where target molecules are collected by attaching to the surface of the pores.

“Since the performance of an electrochemical biosensor depends on the surface area to improve charge transfer and catalytic activity, two-dimensional graphene-like nanomaterials and functionalized graphene are now the best possible materials for a new generation of highly sensitive glucose sensors,” Dr. Singh said. “The holey graphene is very sensitive even at very low concentrations of glucose.”

These fluids are easily accessed without the need for any finger pricking and can be examined to identify various biomarkers, such as those involved in cancer, Alzheimer’s disease, Parkinson’s disease, cystic fibrosis, systemic sclerosis and glaucoma, and blood sugar levels for diabetes management.

When saliva, tears, or sweat hit the surface, the sugars interact with a layer of nitrogenated holey graphene (C2N) that is only a single atom thick. Glucose, fructose and xylose are the sugar molecules found in the body and when they interact with the holey graphene layer, the electronic properties of the layer are altered. These changes are measured and interpreted as various levels of sugar in the bodily fluid tested.

This work was supported by the Swedish Research Council, the Abu Dhabi Department of Education and Knowledge, and Khalifa University of Science and Technology.

Jade Sterling
Science Writer
20 December 2021

The post A New Blood Glucose Monitoring Device Using Holey Graphene appeared first on Khalifa University.

Research into advanced materials at Khalifa University is unlocking a number of new technologies that can be used to generate and store renewable energy more efficiently.

Dr. Nirpendra Singh, Assistant Professor of Physics at Khalifa University, and colleagues recently published three papers that investigate the development of materials with a number of applications for renewable energy.

These papers explore new materials that could help improve the performance of thermoelectric materials capable of converting heat into electricity more efficiently, and sulphur-based batteries with high energy densities that could replace traditional lithium-ion batteries.

Understanding Phonon Dynamics of Copper Pseudohalides

A team consisting of to determine how effective they are in conducting the heat. Their study was published in the journal .��

Phonon transport of materials plays a significant role in determining their thermoelectric performance. Dr. Singh’s team investigated two copper-based compounds – copper thiocyanate (CuSCN) and copper selenocyanate (CuSeCN) – which are candidates for inexpensive large-area photovoltaic use, but until now, have not been deeply studied for phonon transport. The research team comprehensively determines phonon thermal transport with the most sophisticated computational approach available to date. The electron localization function profile is used to explain phonon softening, which was found to be the leading cause of low in-plane lattice thermal conductivity. The high phonon scattering rates in CuSeCN give rise to lower lattice thermal conductivity than CuSCN, suggesting its better thermoelectric performance, Dr. Singh explained.��

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Lead-free Double Perovskite Cs2PtI6: A Promising Thermoelectric Material

While transparent materials are vital for renewable energy harvesting, thermoelectric materials are crucial for turning heat – either heat from the sun or waste heat from power plants and cars – into renewable energy. One promising thermoelectric material is double perovskite Cs2Ptl6, a lead-free hybrid material containing cesium and platinum.��

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Dr. Singh, Dr. Muhammad Sajjad, and Dr. J. Andreas Larsson from the Luleå University of Technology, Sweden, in work recently published in the journal .

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The researchers found that the Cs2Ptl6 shows high thermoelectric performance at and above room temperature and is therefore worth exploring for thermoelectric applications. Cs2PtI6 has a lattice thermal conductivity that is 8-fold smaller than that of the commercial thermoelectric material Bi2Te3. Nanostructuring and alloying of Cs2Ptl6 can lead to further improvement in thermoelectric performance, possibly making it useful for conventional thermoelectric generators.�� For future energy needs, finding alternative and better thermoelectric materials is critically needed, Dr. Singh said.��

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Polar C2N Sheet: A Potential Electrode Enhancer in Sodium–Sulfur Batteries

With clean renewable energy production comes the need for energy storage since renewable energy supply is intermittent. Currently, metal-ion batteries are used, but low energy density and relatively high cost limit their viability for large-scale usage.

Alkali metal-sulfur batteries have emerged as a promising option, especially in applications requiring high energy storage capacity. However, one issue with metal-sulfur batteries is the so-called ‘shuttle effect.’ In the shuttle effect, metal particles called polysulphides dissolve into the battery’s electrolyte and are transported from the sulfur cathode to the metal anode. This results in a reduction in capacity and charging performance of the battery.

Finding a way to suppress the shuttle effect is crucial to metal-sulfur battery performance and lifetime.. They published their findings in the journal.

The 2D materials the team investigated were nitrogenated holey graphene (C2N) and nonpolar polyaniline (C3N). Both C2N and C3N are 2D nanostructures, which can help to anchor the metal polysulphides to the sulfur cathode and improve the electric conduction of the sulphur cathode in metal-sulfur batteries.

The researchers found that C2N was a stronger anchor than C3N, paving the way for a cost-effective C2N nanosheet as an anchoring material for the high-energy and high-capacity batteries needed for large-scale photovoltaic energy storage.

As energy consumption continues to rise, finding new materials that can make renewable solar energy generation and storage cleaner and more efficient will be key to meeting the world’s growing energy demands sustainably.

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Jade Sterling
Science Writer
12 April 2021

The post Getting More Clean Energy with New Materials appeared first on Khalifa University.

A team of researchers have discovered a new way to see organic matter inside of fossilized ‘diatoms’ –�� a type of microalgae – using powerful microscopy imaging techniques, which could help scientists better understand the conditions and climate of the Earth thousands of years ago.

Diatoms are one of the most prolific microscopic sea organisms that serve as food for many animals. Beyond that though, diatoms – which include around 16,000 species – can be preserved in the sediment record, offering clues into what life was like on Earth in the past.����

The extensive fossil record of diatoms in this sediment record is extremely useful to researchers looking at changes in ecological conditions over long periods of time.

The research team includes Dr. Gobind Das, Associate Professor of Physics at Khalifa University, Dr. Shaun Akse, Dr. Lubos Polerecky and Dr. Jack Middelburg from the Department of Earth Sciences at Utrecht University, Dr. Susana Agusti from the Red Sea Research Center and Core Labs at King Abdullah University for Science and Technology, and Dr. Laetitia Pichevin from the School of Geosciences at the University of Edinburgh. Their findings were recently published in.

Diatoms’ unique anatomy features a cell wall made of hydrated silicon dioxide, or amorphous silica, called a frustule. Fossil evidence suggests that certain fossil diatoms originated during or before the early Jurassic period, which was about 150 to 200 million years ago.

This silica is thought to protect any organic matter in the fossilized diatom, which could be investigated to understand and reconstruct the conditions of the oceans at the time the diatom was alive.

“Scientists believe that nitrogen encased in the diatom frustule is protected from any alteration, presenting a more robust insight to the conditions of that time period,” explained Dr. Das.

However, the location of this organic matter within the frustule has proved challenging to identify­—until now.

Using high spatial resolution imaging techniques, the research team identified where the organic material is retained in the fossil. They developed and applied nanoscale secondary ion mass spectrometry (nanoSIMS imaging), which allows imaging of elements down to 50 nanometres.

To validate their findings, they used microRaman spectroscopy and transmission electron microscopy (TEM) to probe further into the fossil and identify the molecular structure of samples. While the TEM technique did not have the sensitivity to image the organic material, the nanoSIMS and Raman techniques imaged the presence of organic matter in fossil frustules for the first time, highlighting exactly where the organic matter can be found.

Diatoms build intricate hard but porous frustules, which are highly patterned with a variety of pores, spines, ridges and elevations. The samples used for the research team’s investigation came from a core of sediment that was 12,450 years old.

“Our findings suggest that organic signals were present throughout the frustule but in higher concentrations at the pore walls,” said Dr. Das.

“As the first result of its kind, our study shows that the organic material embedded in the silica matrix of fossil frustules can be imaged, but the nanoSIMS analysis should be combined with additional high spatial resolution chemical mapping techniques to confirm and better understand the distribution of organics within the frustule of fossil diatoms.”

Finding the organic material in these fossils allows further and more accurate investigation into its composition, which will help researchers understand more about the atmospheric and oceanic conditions of life on Earth more than 12,000 years ago.��

Jade Sterling
Science Writer
23 March 2021

The post Imaging Organic Matter in 12,000 Year Old Fossils for the First Time appeared first on Khalifa University.