New review paper published in Industrial Chemistry & Materials on utilizing the electrochemical quartz crystal microbalance (EQCM) to better understand the charge/discharge processes in supercapacitors.

Supercapacitors are renowned for their exceptional attributes, including high power density, fast charging capabilities, and remarkable cycling stability. To further enhance their potential, it is crucial to comprehend the intricacies of their charging processes. The EQCM, with its nanogram-level in situ mass change information, has played a pivotal role in unraveling these mechanisms.

Our paper provides a comprehensive review of the progress made in EQCM, covering theoretical fundamentals and its applications in supercapacitors. We also delve into the fundamental effects of ion desolvation and transport, shedding light on their impact on supercapacitor performance.

By thoroughly examining the advantages and limitations of EQCM in supercapacitors, we present a holistic view of this groundbreaking technique. Moreover, we propose future directions for further exploration in this dynamic field.

This work was done in collaboration with our long-time collaborator Guang Feng from the Interface and Transport Phenomena (ITP) Laboratory at Huazhong University of Science and Technology (HUST).

Lei Wang has successfully defended his Ph.D. thesis “Faradaic materials and processes for the electrochemical separation of alkali and alkaline earth metal ions”. Congratulations, Dr. Wang!

New paper published in Advanced Materials Interfaces on mechanisms in high-performance tin oxide / MXene batteries. As the demand for power and energy storage continues to grow, we researchers are constantly exploring new ways to improve battery performance. One promising approach involves using conversion/alloying materials, such as tin oxide, to design high-performance lithium-ion batteries. While these materials show excellent performance and ease of preparation, they often suffer from mechanical instabilities during cycling that limits their usefulness. This issue can be addressed (and overcome) by combining tin oxide with MXene.
In this study, we prepared a 50/50 (by mass) tin oxide / Ti-MXene (SnO2/Ti3C2Tz) nanocomposite and optimized it as a negative electrode for lithium-ion batteries. The result? A nanocomposite that delivers over 500 mAh/g for 700 cycles at 0.1 A/g and demonstrates excellent rate capability, with 340 mAh/g at 8 A/g.
The success of this nanocomposite lies in the synergistic behavior of its two components, which we confirmed through ex situ chemical, structural, and morphological analyses. Not only does this knowledge allow us to formulate a reaction mechanism with lithium-ions that provides partial reversibility of the conversion reaction, but it also opens up new possibilities for designing high-performance lithium-ion batteries.

Thanks to our great team of collaborators:

Team Ricerca sul Sistema Energetico – RSE SpA & Università degli Studi di Milano-Bicocca:
Antonio Gentile
Chiara Ferrara
Stefano Marchionna
Riccardo Ruffo

Team INM-Leibniz Institute for New Materials:
Stefanie Arnold
Volker Presser

Team Karlsruhe Institute of Technology (KIT)
Yushu Tang
Julia Maibach
Christian Kübel

New paper published in Applied Catalysis B: Environmental which explores a promising new approach to resource recovery and wastewater treatment. Nitrate is widely distributed in industrial wastewater and contaminated water bodies, and electrochemically converting it into ammonia holds great potential. At the same time, the treatment of harmful algal blooms (HABs) presents a significant challenge worldwide. It’s time-consuming, resource-intensive, and has a high CO2 footprint. But what if we could see this carbon and nitrogen-rich biomass as a vast renewable resource, rather than disposable waste? That’s precisely what we set out to do.

Within our Sino-German collaboration, we developed a Fe-dispersed carbon-based catalyst derived from HABs biomass. The resulting material achieved a maximum ammonia yield rate of 16449 μg/h/cm2 (1.2 mmol/h/mg_cat) and NH3 Faradaic efficiency of 87.3%. Furthermore, the catalyst demonstrated excellent stability, with continuous operation over 50 hours. Our experimental and theoretical calculation results suggest that the Fe-N4 site facilitates the electrocatalytic nitrate reduction reaction by reducing the energy barriers of the NO3-to-NH3 pathway.

We believe our strategy of upcycling HABs biomass waste into functional catalysts represents a significant step forward in renewable and carbon-neutral energy technologies. We are grateful for the opportunity to contribute to this field and are excited to continue exploring new solutions to some of our most pressing environmental challenges.

This work was a collaboration with our Chinese colleagues from Jiangnan University (He Wang, Shuaishuai Man 满帅帅, Han Wang, Qun Yan) and Jiangsu Hongqi Biotechnology (Yong Zhang).

New paper published in npj Materials Degradation (open access). In cooperation with the group of Frank Mücklich at Saarland University and partners, we have found that coating laser-patterned stainless-steel surfaces with carbon nanotubes (CNT) or carbon onions (CO) can create an effective solid lubrication system. By storing the particles inside the pattern, lubricant retention is improved and depletion in the contact area is prevented. In previous works, we used laser interference patterning to create line patterns with different depths and coated them with CNTs or COs. Friction tests were conducted to study the effect of structural depth on the lubricity of these surfaces, and we found that shallower textures result in lower friction coefficients. Our latest study examines the degradation of the carbon nanoparticles on substrates with different structural depths, and Raman characterization shows severe degradation of both particle types. This degradation is classified within Ferrari’s three-stage amorphization model. Electron microscopy also confirms that CNT lubricity is improved at the cost of increasing particle defectivity, while CO-derived tribofilms experience even more substantial structural degradation.

Welcome new postdoc Dr. Gracita Tomboc! With past experience at Myongji University, Korea University, and Université du Québec à Trois-Rivières, we are excited about our upcoming joint work on energy and electrochemistry.

Welcome new AMASE Students Peter Burger and Maria Holmström! AMASE is an international Master’s program and an amazing opportunity to study not just materials science but to do so in multiple European cities! Both will be working on novel materials and methods for electrochemical desalination. Welcome to the team!

New paper published on “Unraveling the Electrochemical Mechanism in Tin Oxide/MXene Nanocomposites as Highly Reversible Negative Electrodes for Lithium-Ion Batteries” in Advanced Materials Interfaces.

As the demand for power and energy storage continues to grow, we researchers are constantly exploring new ways to improve battery performance. One promising approach involves using conversion/alloying materials, such as tin oxide, to design high-performance lithium-ion batteries. While these materials show excellent performance and ease of preparation, they often suffer from mechanical instabilities during cycling that limits their usefulness. This issue can be addressed (and overcome) by combining tin oxide with MXene.

In this study, we prepared a 50/50 (by mass) tin oxide / Ti-MXene (SnO2/Ti3C2Tz) nanocomposite and optimized it as a negative electrode for lithium-ion batteries. The result? A nanocomposite that delivers over 500 mAh/g for 700 cycles at 0.1 A/g and demonstrates excellent rate capability, with 340 mAh/g at 8 A/g.

The success of this nanocomposite lies in the synergistic behavior of its two components, which we confirmed through ex situ chemical, structural, and morphological analyses. Not only does this knowledge allow us to formulate a reaction mechanism with lithium-ions that provides partial reversibility of the conversion reaction, but it also opens up new possibilities for designing high-performance lithium-ion batteries.

Thanks to our great team of collaborators:

Team Ricerca sul Sistema Energetico – RSE SpA & Università degli Studi di Milano-Bicocca:
Antonio Gentile
Chiara Ferrara
Stefano Marchionna
Riccardo Ruffo

Team INM-Leibniz Institute for New Materials:
Stefanie Arnold
Volker Presser

Team Karlsruhe Institute of Technology (KIT)
Yushu Tang
Julia Maibach
Christian Kübel

Our research team has published an article in ChemSusChem on the promising use of stable and efficient SnO2 electrodes for degrading refractory organic pollutants in wastewater treatment. Our approach involved the preparation of Ti3+ self-doped urchin-like rutile TiO2 nanoclusters (TiO2-xNCs) on a Ti mesh substrate using hydrothermal and electroreduction methods, which served as an interlayer for the deposition of Sb-SnO2. Our TiO2-xNCs/Sb-SnO2 anode exhibited a high oxygen evolution potential and strong *OH generation ability, resulting in improved degradation performance for rhodamine B, methylene blue, alizarin yellow R, and methyl orange. Our unique rutile interlayer also extended the anode lifetime sixfold due to its good lattice match with SnO2 and three-dimensional concave-convex structure. Overall, our work highlights the importance of designing interlayer crystal forms and structures for achieving efficient and stable SnO2 electrodes in addressing dye wastewater problems. This work was done in collaboration with our colleagues from Chongqing University.

Welcome new Ph.D. student Liying Xue! Liying is from Guangxi University, China, and will be working on high entropy materials

Welcome to our team, Prof. Dr. Syed Tauqir Ali Sherazi! Having been awarded the prestigious Georg Forster Fellowship of the Alexander von Humboldt Foundation, he will be working on next-generation water remediation technologies. Our visiting Fellow is Professor at COMSATS University Islamabad Abbottabad Campus in Pakistan.

New paper published in the Journal of Industrial and Engineering Chemistry. In cooperation with former group member Choonsoo Kim (now at Kongju University, Korea), we have used redox flow desalination for the valorization of tetramethylammonium hydroxide as a value-added organic compounds from wastewater which is widely being used as an etching solvent, photoresist developer, and surfactant
in semiconductor and display industries. By applying a low cell voltage (<1.2 V), a reversible redox
reaction allowed a continuous removal of TMAH from the wastewater stream and a simultaneous recovery for reuse as a form of tetramethylammonium cation. The TMAH removal rate was approximately
4.3 mM/g/h with a 40% recovery ratio.

New perspective paper published in Communications Materials. The high entropy concept is ideally suited for MXenes but also capable to be a unique tool to tailor and improve electrochemical properties in other materials.

Multiple principal element or high-entropy materials have recently been studied in the two-dimensional (2D) materials phase space. These promising classes of materials combine the unique behavior of solid-solution and entropy-stabilized systems with high aspect ratios and atomically thin characteristics of 2D materials. The current experimental space of these materials includes 2D transition metal oxides, carbides/carbonitrides/nitrides (MXenes), dichalcogenides, and hydrotalcites. However, high-entropy 2D materials have the potential to expand into other types, such as 2D metal-organic frameworks, 2D transition metal carbo-chalcogenides, and 2D transition metal borides (MBenes).

So, what is our perspective article about? We discuss the entropy stabilization from bulk to 2D systems, the effects of disordered multi-valent elements on lattice distortion and local electronic structures and elucidate how these local changes influence the catalytic and electrochemical behavior of these 2D high-entropy materials. We also provide a perspective on 2D high-entropy materials research and its challenges and discuss the importance of this emerging field of nanomaterials in designing tunable compositions with unique electronic structures for energy, catalytic, electronic, and structural applications.

This perspective paper has been the result of our collaboration with my dear friend Babak Anasori (with his team: Kartik Nemani and Brian Wyatt) from Purdue University and our team (including Mohammad Torkamanzadeh).

Joint work is presented by the Gallei Group at the Macromolecular Colloquium Freiburg (MAKRO 2023). Check out our paper with the title “Stabilizing isoporous, self-assembled block copolymer structures in membranes and cellulose hybrid materials” if you attend the event!

Very happy to see both Behnoosh Bornamehr and Mohammad Torkamanzadeh winning in the essay competition on open science / open data of Saarland University! This makes for a 100% win rate for applicants from our team 😉 Open access is not without challenges and caveats and the journey toward a world of true open science remains a high goal for the future. I am happy to see that our students actively engage in the conversation and contribute their valuable insights and share their experience!

New paper published in ACS Applied Nano Materials. Rolling bearings need lubrication to operate smoothly, but when traditional methods fail, multiwall carbon nanotubes (MWCNT) can come to the rescue. To understand how MWCNTs lubricate highly loaded contacts, we combined experimentation and large-scale molecular dynamics simulations. We applied tribometry to iron plates coated with different types of MWCNTs, discovering that both resulted in a steady-state coefficient of friction of 0.18. Wear tracks and tribolayers revealed a transformation process, resulting in layers of MWCNT fragments, iron oxide, and iron carbide nanoparticles embedded in an amorphous carbon matrix. We also found that MWCNTs slide against the ball interface to provide low carbon transfer to the counter body. Molecular dynamics simulations predicted a low-load regime that keeps MWCNTs intact, and a high-load regime that partially collapses the tube structure, forming a-C regions. We confirmed the results through transmission electron microscopy, and formulated a multistep lubrication mechanism for MWCNT coatings rubbing against alumina on an iron substrate. This work was done in collaboration with the teams of Frank Mücklich and Michael Moseler.

New paper published in the Journal of the American Ceramic Society on the synthesis of new hybrid electrode materials for Li-ion batteries (LIBs). Through controlled oxidation of layered Ti2SnC, we were able to obtain TiO2-SnO2-C/carbide hybrid materials using two different methods: partial oxidation in an open-air furnace (OAF) and rapid thermal annealing (RTA). The resulting carbide phase included both residual Ti2SnC and TiC as a reaction product. In testing, we found that the sample oxidized in the OAF at 700°C for 1 hour had the highest initial lithiation capacity of 838 mAh/g at 100 mA/g. However, its delithiation capacity decreased to 427 mAh/g over cycling. In contrast, the RTA sample treated at 800°C for 30 seconds demonstrated the most efficient performance, with a reversible capacity of approximately 270 mAh/g after 150 cycles and a specific capacity of about 150 mAh/g under high cycling rate (2000 mA/g). Our findings suggest that this processing method could have wide-ranging applications in energy storage, particularly for other members of the MAX family. This work was the latest product of collaboration with the team of Michael Naguib (Tulane University, USA).

New paper published in Journal of Energy Storage on MXene battery electrode recycling.

Even the most wonderful electrode material, some sooner than later, will degrade. Even the most wonderful battery, regardless of the used chemistry, will see the end of its life. Battery recycling, using hydrometallurgical or pyrometallurgical pathways, is very energy consuming. So are there alternative recycling concepts? Of course there are! But many of them remain poorly explored.

New materials may not just allow better performance but also novel recycling and second-life applications. The diverse 2D material MXene, for example, can be processed into battery electrodes without binder and without conductive additive. It does not need them 😉 With 100% active mass, and associated with a 2D material, MXene is an ultimate case for an assembly-disassembly-reassembly material. Our work shows the benefits (and limitations) to this circularity of MXene batteries for lithium-ion and sodium-ion batteries.

But sometimes, even with the most heartfelt effort, recycling has its limits. No worries, though, MXenes can also have a second-life! If you oxidize materials, such as titanium based MXene, you end up with metal oxide & carbon (carbide) hybrids that show promising applications for electrocatalysis (or other energy applications).

More MXene and more recycling works upcoming! Stay tuned and I hope more people start not just exploring fancy battery materials but also what to do with spent electrodes. Only time will tell which approach will master upscaling and economic challenges but we, as scientists, must explore all possible pathways.

Big shoutout to my former Ph.D. student Yunjie Li (now in Ulm with Dominic Bresser), our Ph.D. student Stefanie Arnold, and our former Postdoc Dr. Samantha Husmann (now in industry).

New paper published in ChemSusChem in collaboration with the Kickelbick-Group at Saarland University. We have developed an exciting new class of inorganic-organic hybrid materials with redox-active components that have great potential for use in lithium-ion batteries (LIBs). The materials were prepared using an aqueous precipitation reaction of ammonium heptamolybdate (AHM) with para-phenylenediamine (PPD), and a low-energy continuous wet chemical synthesis process known as the microjet process. By varying the ratio of molybdate to organic ligand and pH, we were able to produce two different crystalline hybrid products with large surface areas in the submicrometer range and high purity and reproducibility on a large scale. The first product, [C6H10N2]2[Mo8O26] ⋅ 6 H2O, was obtained by using a ratio of para-phenylenediamine to ammonium heptamolybdate from 1 : 1 to 5 : 1. The second product, [C6H9N2]4[NH4]2[Mo7O24] ⋅ 3 H2O, was obtained by using higher PPD ratios from 9 : 1 to 30 : 1. Our electrochemical testing revealed that the second product showed exceptional battery performance, with a high capacity of 1084 mAh/g at 100 mA/g after 150 cycles. The product reached maximum capacity after an induction phase, which can be explained by a combination of a conversion reaction with lithium to Li2MoO4 and an additional in situ polymerization of PPD. We are excited about the potential of this hybrid material for use in LIB applications.

Volker Presser was honored for the work on electrochemical water remediation and Lithium-ion extraction by the City of Saarbrücken. Read more about the event and all awardees.