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 Electrochimica Acta on Ni-decorated AgAu alloy graphene/cobalt hydroxide electrodes for micro-supercapacitors to obtain high-performance micro-supercapacitors. A nanocomposite of graphene, cobalt hydroxide and nickel can was obtained from using gold-silver alloy lines. Using a two-step electrodeposition method, the scaly morphology is pre-deposited on a Ni film, followed by the interconnecting corrugated graphene/cobalt hydroxide composite nanomaterial. The resulting device, a graphene/cobalt hydroxide/Ni//activated carbon flexible micro-supercapacitor (MSC), was assembled by gel KOH-PVA electrolyte, graphene/cobalt hydroxide/Ni (positive electrode), and activated carbon (negative electrode). When testing, we obtained a volumetric energy of about 19 mWh/cm³ and the devices retained over 94% capacitance after 10,000 cycles. After 1,000 continuous bending/unbending cycles at a 180° bending angle with the frequency of 100 mHz, the capacitance retention of MSC is still maintained at 97% of the initial value.

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 published in Current Opinion in Green and Sustainable Chemistry on “Recent advances in wastewater treatment using semiconductor photocatalysts”. Can’t decide if you like water remediation or photocatalysis/semiconductors more? They both make a great match! Read about synergies and future possibilities in our latest review article in Current Opinion in Green and Sustainable Chemistry. The team of Prof. Xiao Su (Jaeyoung Hong & Ki-Hyun Cho) and I explore this interesting interfacial research – interfacial in double meaning: at the interface of fluid and solid, and at the interface of material science/electrochemistry and water research. It is exciting to explore semiconductors, for example, to target emerging contaminants, such as perfluorinated compounds.

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 Advanced Sustainable Systems on the ion selectivity of MXene electrodes during electrochemical operation. The Tortoise and the Hare is a classic Aesop fable that we heard growing up. We learned that a clever strategy could win over physical advantages in any match of unequal rivals. In the day and age of MXene, this fable returns when we explore MXenes as an electrode material for ion separation. The structure of MXenes impacts ion preference, as was shown before. For example, Amir Razmjou’s team wonderfully investigated the d-layer spacing’s effect on ion selectivity (10.1016/j.memsci.2021.119752). Our work now explores the ion exchange within the nanoconfined electrolyte space provided by MXene layers. We see that monovalent ions like potassium are initially preferred – only to be replaced over time by bivalent ions, like Magnesium. MXene behaves thereby like carbon nanopores, for which such ion exchange processes during continued charging were demonstrated before, among others, by the team of Maarten Biesheuvel (10.1016/j.jcis.2012.06.022). The combination of kinetic and intrinsic ion selectivity may enable novel applications within the energy/water research nexus. However, a higher ion selectivity will have to be enabled for industrial applications.

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 Nature Energy entitled “Continuous transition from double-layer to Faradaic charge storage in confined electrolytes”. Our paper explores the fascinating world from ion electrosorption transitioning towards Faradaic processes when electrolytes are nanoconfined. This work was a collaboration with several groups, espcially the team of Veronica Augustyn (NC State), Yury Gogotsi (Drexel), Patrice Simone (Toulouse) and more.