Scientific Events

Host: on invitation of Prof. Dierk Raabe

Prussian blue and its derivatives: towards sustainable next-generation energy storage

Portable and stationary rechargeable batteries are within the many energy-related technologies that require fast progress within the urgent need of remediation of global climate. For example, batteries can still represent up to a third of electric vehicles emissions due to their manufacturing process and lack of end-of-life management. Developing fundamentally sustainable battery materials and electrode processing stands as a central strategy for efficient battery recycling. One essential requirement of next-generation battery technologies is the substitution of costly elements like Li and Co by widely (and more evenly) available ones like Na and Fe in the electrode materials. This implies the development of new energy storage materials, as well synthetic methods. Materials with porous and hollow morphologies are one of the promising approaches in achieving long-term stability in batteries. Such structures can buffer volumetric changes associated with many energy storage mechanisms (like conversion reactions or ion insertion), avoiding effects like aggregation, structure collapse and loss of conductivity which leads to poor electrochemical performance. Prussian blue (PB, KFe[Fe(CN)6]) and its analogues (PBA, AM[M’(CN)6]) are cheap, easy to synthesize, non-toxic, biocompatible, water and air-stable metal complexes. They have an intrinsic porous framework structure that allows ion intercalation with very little or no strain. Their metal centers are electroactive in both organic and aqueous media. Therefore, this class of materials is ideal for battery electrode applications, achieving high stability and capacity without the need for complex synthetic routes. The tunability of PB(A) structure and composition also makes them versatile template materials. Through different derivatization methods, PB derivatives (PBD) can be prepared. Regardless of the relatively simple structure of PB(A), PBDs present an ever-growing number of compositions that encompass metal oxides, sulfides, phosphides, carbides, hybrids (among others), and an array of morphologies from simple cubes to highly complex hollow and porous structures. Such PBD have recently demonstrated state of the art performance in catalysis and energy storage applications. This talk will give an overview of the current challenges and strategies to achieve high-performance sustainable batteries, with a focus on PB- and PBD-based electrode materials. [more]

Recovery and Utilization of Materials from electronic waste via Cryomilling to Develop Advanced Green Technologies

Recovery and Utilization of Materials from electronic waste via Cryomilling to Develop Advanced Green Technologies Krishanu Biswas#Electronic waste (e-waste) causes enormous societal and environmental impact when they enter the trash stream. It has emerged as the fastest-growing waste source in recent decades throughout the universe. The global accumulation of e-waste is expected to reach 74 Mt by 2030, nearly doubling in tonnage over this decade (2020-2030). The act of indiscriminate e-waste dumping, along with inefficient and unorthodox e-waste handling, is indisputably detrimental to economic and public health. Since e-waste has dramatically increased the impact on the environment, developing sustainable solutions for recovery and recycling is of prime importance. In this direction, the present research aims to establish an easily scalable and novel green technique to rejuvenate and effectively use metallic, ceramic and polymeric components of the e-waste by use of cryo-grinding in an ecologically responsible and energy-efficient manner. The low-temperature grinding method that breaks down PCBs all the way into nanoscaled particles, further enabling enhanced physical separation of the different base constituent materials that are the polymer, oxide, and metal. The recovered materials are easy to be beneficiated as the nanoscale particles produced from grinding are mostly single phase particles, compared to the larger particles obtained by other methods that are multiphase mixtures of various constituents. The metallic content is utilized to electrochemically selectively reduce CO2 into distinct gaseous products, resulting in the generation of CH4, and H2 as main gaseous products at neutral pH. On the other hand, the extracted polymeric component is utilized to synthesize graphene/CNT using pulsed laser ablation (PLA) in a liquid media, showing promise in synthesizing high-quality graphene, which may be enhanced further by tweaking the PLA process parameters. The synthesized graphene was utilized to fabricate highly conductive electrical connections, revealing the excellent functional capacity of crystalline graphene. Polymeric content along with ceramic are being utilized for making electrical switch boards. In a nutshell, this green technique provided means of extracting main components from e-waste, via low temperature grinding, which can then be utilized to make green energy, precious materials like graphene/CNT, and other engineering applications in an ecologically responsible manner, making the process sustainable and hence, solving a global problem. [more]
Electrochemical energy storage is the key enabling component of electric vehicles and solar/wind-based energy technologies. The enhancement of energy stored requires the detailed understanding of ionic transport and electrochemical and electromechanical phenomena on local scales which are not always accessible with classical electrochemical techniques, such as voltammetry. Therefore, local probing of electrochemical and electromechanical behaviors on individual structural elements and heterogeneities, from grains to defects and further to individual atomic and molecular species, are invaluable. In this talk, I want to introduce force-based atomic force microscopies (AFM) to provided novel insights into local electrochemical processes on tens of nanometer and even molecular length under electrochemical control. I will highlight the development and application of in situ/operando force-based AFM methods to gain insight into the local charge storage mechanism in a variety of energy related materials. In the first part of the talk, I will showcase how AFM can be used to investigate the structure and dynamics of the electric double layer (EDL) for electrochemical capacitors. I want to highlight work on room temperature ionic liquids on model graphene electrodes since ionic liquids hold the promise of increasing the electrochemical stability windows for electrochemical capacitors. AFM was used to observe topological defects and show the existence of structural domains parallel to the solid-liquid interface towards a full picture of the double layer structure and their change with applied bias. In the second part of the talk, I want to highlight how AFM-based methods can be used to study ionic transport and local electrochemical reactions in supercapacitors and battery materials. Here, electro-chemo-mechanical coupling is the key to study ion insertion pathways and heterogeneities in local redox reactions. The first is demonstrated for the cation insertion into layered Ti3C2 electrodes based on their change in mechanical stiffness whereas the second is highlighted for proton insertion into WO3 where the relationship between electrochemical current and electrode strain are discussed. [more]
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