Archive for category: Publications

New paper in Carbon on hydrogen densification in carbon nanopore confinement: Insights from small-angle neutron scattering using a hierarchical contrast model from our long-term collaboration with Oskar Paris (Montanuniversität Leoben).

New battery published in ACS Applied Materials & Interfaces on hybridization of carbon spherogels with titanium oxide and sulfur enables high performance lithium-ion battery electrodes. As a result from our research project with Michael Elsaesser from the Paris Lodron Universität Salzburg, we introduce a novel approach to enhancing lithium-ion battery electrodes. We have successfully combined titanium oxide and sulfur with carbon spherogels, achieving high performance in terms of stability and capacity. Our method resulted in electrodes combining high charge storage capacity and electrical conductivity, while maintaining a core-shell morphology. The process involved producing carbon spheres encapsulating titania and sulfur using a template-assisted sol-gel route, followed by thermal treatment with hydrogen sulfide gas. This treatment fully preserved the microporous hollow sphere architecture of the carbon shells, facilitating sulfur deposition and titania crystal protection.

New paper published in Energy Advances from our continued collaboration with Michael Elsaesser (Paris Lodron Universität Salzburg) on carbon spherogels. Custom-designed nanoporous carbon materials enhance sustainable electrochemical technologies by offering better performance and efficiency. Carbon spherogels, which are highly porous carbon aerogel materials made up of a network of hollow carbon nanospheres with consistent diameters, are particularly promising. They offer unique advantages, including superior electrical conductivity, customizable porosity, adjustable shell thickness, and extensive surface area. In this work, we present a new, eco-friendlier approach to producing carbon spherogels using a sol-gel process that templates resorcinol-formaldehyde (RF) with polystyrene spheres in an organic solvent. By adjusting the molar ratio of resorcinol to isopropyl alcohol (R/IPA) and the polystyrene concentration, we identified the optimal conditions for creating carbon spherogels with tunable wall thicknesses. A simplified solvent exchange method from deionized water to isopropyl alcohol was developed to reduce surface tension in the gel’s pores, making this method both time and cost-efficient. The use of isopropyl alcohol, with its lower surface tension, allows for solvent extraction at room temperature and direct carbonization of RF gels with less than 20% loss in specific surface area compared to those dried supercritically. The resulting materials have specific surface areas ranging from 2300 to 3600 m²/g, as confirmed by transmission and scanning electron microscopy, which also demonstrated their uniform, hollow spherical network structure. Notably, these carbon spherogels act as high-performance electrodes for energy storage in supercapacitors, achieving a specific capacitance of up to 204 F/g at 200 mA/g with a 1 M potassium hydroxide (KOH) solution as the electrolyte.

New paper published in Journal of Molecular Liquids on binary ionic liquid supercapacitors. There is much to learn from simulation when it comes to understanding nanoscaled ion electrosorption of ions within carbon nanopores. Especially when it comes to the behavior of ionic-liquid-based supercapacitors which promise an extended potential window, and consequently, enhanced energy ratings. Ionic liquids, in absence of a solvent, and with enhanced ion-ion interactions, present an intriguing model system to study size effects in more complex electrolytes with more than just one cation. Our findings, combining simulation and experimental data, reveal the enhanced capacitance of single nanopores and nanoporous electrodes using binary electrolytes. 🔬⚡
I’d like to extend my heartfelt gratitude to our research partners (Taras Verkholyak, Dariusz Gołowicz, Andrij Kuzmak, Svyatoslav Kondrat) and my team (Anna Seltmann, Emmanuel Pameté)! And I am proud to share that this is a collaborative Polish 🔴⚪ German ⚫🔴🟡 Ukrainian paper 🔵🟡.

New paper published in Advanced Functional Materials in lead by the teams of Michael Naguib and Agnieszka Maria Jastrzębska. MBenes, a new class of post-MXene materials, stand out due to the inclusion of boron in their structure, replacing carbon and nitrogen. This distinct composition provides a fresh perspective on boron’s impact in two-dimensional materials. The challenge in processing MBenes lies in the wet-chemical etching and delamination of the initial MoAlB phase, mainly due to the strong bonding of aluminum with surrounding elements. This research successfully addresses this challenge by treating MoAlB with an aqueous HCl/H₂O₂ solution for varying durations of 24 hours, 48 hours, and 72 hours. The process results in individual, single-to-few layered MBene flakes, particularly notable in the 48-hour etched sample. Detailed analysis through a combination of theoretical and experimental X-ray diffraction techniques reveals that the optimally delaminated 48-MBene possesses a Mo2B2 orthorhombic lattice structure. Additionally, the formation of Mo oxide within these MBenes introduces both direct (1.2 eV) and indirect (0.2 eV) optical band gaps, significantly enhancing their photocatalytic efficiency. This is especially evident in their ability to decompose methylene blue, a commonly used organic pollutant, achieving about 90% decomposition under UV and simulated white light, with a rate thrice as fast as some MXene hybrids. Moreover, the 48-MBene shows exceptional capability in harnessing the full spectrum of visible light to generate reactive oxygen species. In contrast, the 24-hour and 72-hour treated MBenes exhibit lesser performance due to incomplete delamination or oxidation. These findings pave the way for using MBenes in environmental cleaning applications, highlighting their potential in addressing water contamination issues.

New paper published in ACS Nano. Our work explores horn-like pore entrance geometries that boost the overall charging dynamics and charge storage of nanoporous supercapacitors. This work was in collaboration with Guang Feng (HUST).

New review article published in Advanced Energy Materials on the degradation of supercapacitors, as featured as “Editor’s Choice” and on the front cover.

Our review discusses the significance of monitoring methods and strategies for tracking the performance degradation of EDLCs and pseudocapacitors, employing a range of cutting-edge techniques such as electrochemical methods and in situ and ex situ analyses. These methods enable researchers to better understand the underlying mechanisms behind supercapacitor aging.

We also explore the intricate interplay of electrode materials, electrolytes, and other critical system aspects, including pore blocking, electrode compositions, functional groups, and corrosion of current collectors. When we understand these factors, we can pave the way for enhanced supercapacitor designs and materials that offer prolonged lifespan and improved performance. Moreover, we also examine the impact of aging from an industrial application standpoint, providing valuable insights into the real-world scenarios. And finally, we highlight future directions and challenges, including the development of innovative materials and advanced monitoring methods, to combat performance degradation effectively.

Team INM-Leibniz Institute for New Materials: Emmanuel Pameté, Volker Presser
Team Friedrich Schiller University Jena: Lukas Köps, Fabian Kreth, Andrea Balducci
Skeleton Technologies: Sebastian Pohlmann
Helmholtz Institute Ulm (HIU): Alberto Varzi
Nantes Université: Thierry Brousse

New paper published on iron vanadate derived from Prussian Blue analog for Lithium-ion batteries in Sustainable Energy & Fuels. This marks our latest work on derivatization strategies to turn Prussian Blue Analogs (PBAs) into mixed metal oxide materials for battery applications 🔋

🔹We used PBAs as they offer a very high tunability and ease of synthesis.
🔹We successfully achieved homogeneous iron vanadate derivatization using an energy-efficient infrared furnace with CO2 gas.
🔹We entangled the active material with carbon nanotubes to generate binder-free, free-standing electrodes for direct use as electrodes.
🔹We stabilized the electrochemical performance reaching a 400 mAh/g capacity at a specific current of 250 mA/g after 150 cycles, maintaining a Coulombic efficiency of 99.2% in a potential range of 0.01-3.5 V vs. Li/Li+.
🔹The choice of electrolyte matters (of course) also, with a better performance in Li-TFSI in carbonate electrolyte compared to Li-PF6.

For an in-depth understanding of our methodology and findings, I encourage you to read the full paper where we delve deep into the role of different surfactants and the optimization of various parameters for a stable electrochemical performance.

New paper published on hydrogel-based flexible energy storage in Advanced Materials Interfaces. Our study showcases a novel electrolyte system that stands out due to its flexibility, electroactivity, and improved sustainability.
We initiated our research by electropolymerizing polypyrrole (PPy) nanotubes in graphite-thread electrodes, utilizing methyl orange templates in an acidic medium. This process successfully enhanced the conductivity, while maintaining the flexibility of the electrodes, a crucial component in developing versatile energy storage systems. We built flexible devices using hydrogel as an electrolyte prepared from poly(vinyl alcohol) (PVA)/sodium alginate (SA). This hydrogel was obtained through freeze-thawing and swelling with ionic solutions. The result was a homogenous and porous hydrogel matrix, demonstrating high conductivity of 3.6 mS/cm as-prepared and the ability of self-healing.

What sets this material apart is its adaptability. The material’s electrochemical and mechanical properties depend on the swollen electrolyte used, allowing its integration with the modified graphite-thread electrodes. This flexibility led us to develop a quasi-solid electrochemical energy storage device, with a specific capacitance value of 66 F/g at 0.5 A/g. The choice of less environmentally friendly acid electrolyte HNO₃ yielded a higher capacitance in the range of 100 F/g. These attributes relied on the liquid phase in the hydrogel matrix produced from biodegradable polymers.

We thank our collaborators who were instrumental in this research project. Special acknowledgment to our esteemed colleagues from the Departamento de Química, Universidade Federal do Paraná in Brazil: Andrei Elias Deller, Izabel C. Riegel-Vidotti, and Marcio Vidotti. On our team, we are grateful for the contributions of Ph.D. student Jean Gustavo De Andrade Ruthes, our postdoc and Humboldt-Fellow Emmanuel Pameté.