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 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 Carbon. This is our latest work from our collaboration with our Austrian partners now being published in the January issue of Carbon. Combining the expertise in catalysis of the Eder group (TU Vienna) with the innovative carbon spherogel material developed by Michael Elsaesser from the Hüsing Group (Paris Lodron Universität Salzburg) makes up for an interesting system. Spherogels are hollow carbon spheres which, as shown by this work, can be conveniently loaded with electrocatalytically active species, such as titania. In our case, we studied the photocatalytic hydrogen evolution.

New paper published in ACS Omega. Batteries employing transition-metal sulfides enable high-charge storage capacities, but polysulfide shuttling and volume expansion cause structural disintegration and early capacity fading. The design of heterostructures combining metal sulfides and carbon with an optimized morphology can effectively address these issues. Our work introduces dopamine-coated copper Prussian blue (CuPB) analogue as a template to prepare nanostructured mixed copper–iron sulfide electrodes. The material was prepared by coprecipitation of CuPB with in situ dopamine polymerization, followed by thermal sulfidation. Dopamine controls the particle size and favors K-rich CuPB due to its polymerization mechanism. While the presence of the coating prevents particle agglomeration during thermal sulfidation, its thickness demonstrates a key effect on the electrochemical performance of the derived sulfides. After a two-step activation process during cycling, the C-coated KCuFeS₂ electrodes showed capacities up to 800 mAh/g at 10 mA/g with nearly 100% capacity recovery after rate handling and a capacity of 380 mAh/g at 250 mA/g after 500 cycles.

new paper published in ACS Energy Letters on continuous electrochemical lithium-ion extraction. We used a redox electrolyte “engine” to drive the ion transfer (in our case: potassium ferricyanide). Employing a pair of ceramic lithium superionic conductor (LISICON) membranes meant that only Lithium ions were accessible to the redox electrolyte for charge compensation. And to complement the design, we used an anion exchange membrane to separate the inflow (e.g., seawater) from a recovery solution. By this way, we obtained an electrochemical system for the continuous extraction of Lithium ions. This sets this technology apart from earlier works (including our contributions) that relied on a cyclic operation to obtain ion separation. Yet, this is just one of many more steps towards seeing such technology toward application; future research must critically address cell design, optimization of the Li-membranes, and investigating the robustness and durability of continuous operation.

This work was the result of the collaboration of our Ph.D. students Lei Wang, Stefanie Arnold, Panyu Ren, and our former Postdoc (now group leader at Bavarian Center for Battery Technology (BayBatt)) Qingsong Wang, as well as our Chinese collaborators Jun Jin and Zahoyin Wen (Chinese Academy of Sciences).

New paper published in Desalination on the ion selectivity of carbon nanopores. It is well known that electrolyte confinement inside carbon nanopores strongly affects ion electrosorption in capacitive deionization. A thorough understanding of the intricate pore size influence enables enhanced charge storage performance and desalination in addition to ion separation. In subnanometer pores, where the pore size is smaller than hydrated ion size, a dehydration energy barrier must be overcome before the ions can be electrosorbed into the pores. Ion sieving is observed when the dehydration energy is larger than the applied energy. However, when a high electrochemical potential is used, the ions can desolvate and enter the pores. Capitalizing on the difference in size and dehydration energy barriers, this work applies the subnanometer porous carbon material, and a high electrochemical ion selectivity for Cs⁺ and K⁺ over Na⁺, Li⁺, Mg²⁺, and Ca²⁺ is observed. This establishes a viable way for selective heavy metal removal by varying pore and solvated ion sizes. Our work also shows the transition from double-layer capacitance to diffusion-limited electrochemical features in narrow ultramicropores.

New paper entitled “Spray-dried pneumococcal membrane vesicles are promising candidates for pulmonary immunization” published in the International Journal of Pharmaceutics. This collaborative work spearheaded by experts from the Helmholtz Institute for Pharmaceutical Research Saarland (HIPS) and Saarland University explores optimized vaccine microparticles with a mean particle size of 1–2 µm, corrugated surface, and nanocrystalline nature.

New paper published in the Journal of Materials Chemistry A. Our work entitled “Design of high-performance antimony/MXene hybrid electrodes for sodium-ion batteries” explores the synergy of the 2D nanomaterial MXene (conductive, nanotextured) and antimony (large sodium-ion storage capacity via alloying). This work is the latest outcome of our collaboration with the group and team of Riccardo Ruffo (Università degli Studi di Milano-Bicocca) and Stefano Marchionna (Ricerca sul Sistema Energetico). Special thanks to visiting Ph.D. student Antonio Gentile from Riccardo’s team!

New paper published in Chemical Engineering Journal. The work with the title “Electro-assisted removal of polar and ionic organic compounds from water using activated carbon felt” was done in collaboration with the Department of Environmental Engineering at the UFZ site in Leipzig.

New paper published in Advanced Energy Materials. Our work used densely carboxylated but conducting
graphene derivative (graphene acid) to enable effective operation without compromising the mechanical or chemical stability of the electrode. In our studies, we found a maximum performance of 800 mAh/g at a rate of 0.05 A/g and 174 mAh/g at 2.0 A/g. This Czech-German work was done in strong collaboration especially with the team of Aristides Bakandritsos from the Technical University of Ostrava.