Transferring Electrochemical CO2 Reduction from Semi-Batch into Continuous Operation Mode Using Gas Diffusion Electrodes

The electrochemical reduction of C02 is a promising method for its conversion which still suffers from important challenges that have to be solved before indus­ trial realization becomes attractive. The optimization of gas diffusion electrodes is described with respect to catalyst dispersion and mass transport limitations allowing solubility issues to be circumvented and current densities to be increased to industrially relevant values. The transfer of the promising results from semi-batch experiments into continuous mode of operation is demonstrated, and it is indi­cated how the energetic efficiency can be significantly improved by the choice of electrolyte, in terms of concentration and type. Thereby ohmic losses can be decreased and the intrinsic activity be improved

Development and Optimization of Gas Diffusion Electrodes for Electrochemical CO2 Reduction at High Current Density

The electrochemical reduction of CO2 to valuable compounds is a promising approach for its substantial utilization and the storage of electricity in chemical form. At present, the main challenges impeding technical realization are i) low production rates due to mass transport limitations deriving from the low solubility of CO2 in the electrolyte, ii) high overpotentials and poor energetic efficiency, necessitating development of more active catalysts, as well as iii) the demonstration of its continuous production which combines the above with low ohmic losses and long-term stability. Furthermore, hydrogen evolution occurs in the same potential range, and becomes dominating at current densities above 10 mA∙cm 2 on conventional metallic electrodes when diffusion of CO2 to the electrode surface becomes rate-determining

Empfindlichkeit der Auslegung von Hybrid-Elektrischen Flugzeugen gegenüber Verbesserungen in der Brennstoffzellen- und Batterietechnologie

Estimations of future developments in fuel cell and battery technology exhibit a high uncertainty but might be relevant to evaluate suitable hybrid electric aircraft configurations. Improvements in power source and energy storage technologies can shift the optimal power source configuration for a given flight mission, provided that all accompanying system considerations are accounted for. To assess the influence on battery and fuel cell developments a sensitivity analysis based on public literature values for current and future specific energies is carried out. Using an in-house simulation model, various fuel cell & battery load-sharing combinations are compared, altering how much power is provided by each subsystem. As a benchmark we use 2 different mission profiles of the same 70-seater aircraft with entry into service in 2040. These mission profiles exhibit different characteristics of climb versus cruise power demand. This demonstrates the possible use-case of complementing a fuel cell-powered aircraft with a battery for high-power segments of the mission. Furthermore, the influence of future improvements in specific energy of battery- and fuel cell systems is assessed. Here we try to determine limits and opportunities for each technology. These results are then compared to current technology roadmaps from literature

Innovative hybrid high voltage electrodes based on LMNO/LFP materials for lithium ion batteries

Nowadays the markets of electric vehicles (EV) and energy storage devices are fast increasing pushing a constant increase in the demand for greener and more sustainable power sources. In particular, for EVs applications, batteries guaranteeing long cycle life combined with high specific energy and high power density are needed. To increase the specific energy, one solution is to increase the cell voltage and the capacity. For this reason, combine high voltage cathode, i.e. LMNO (Lithium Manganese Nickel Oxide), together with high capacity anodes, i.e silicon, can be an interesting solution. Unfortunately, LNMO suffers easy cation leaching during cycling, in particular at high C-rates. The present work shows results achieved within HYDRA H2020 project based on the synthesis of new blended materials combining LMNO and LFP (Lithium Iron Phosphate) in order to match their inherent positive characteristic to get better performing electrodes. LFP was chosen because of its outstanding thermal and electrochemical stability, as well as its Li-redox activity at a relatively high voltage [1][2][3]. Therefore, the presence of the LFP should increase the cycling stability of the LMNO, especially at higher current rates. In order to get a homogeneous coating of LFP particles on the LMNO surface, we used ball milling treatments modifying all parameters, such as frequency, time, and weight percent of LFP. The blended active materials were thus characterized from a morphological and structural point of view with FESEM and XRD analysis, and electrochemical characterization: galvanostatic cycling and cyclic voltammetry studies. The results obtained are showing that the mixing through ball milling does not significantly damage the structure of the two pristine materials and ensures a homogeneous dispersion of LFP particles which partially cover the LMNO particles. The electrochemical data confirm that both materials actively contribute to the capacity of the blended electrodes. Authors kindly acknowledge Hydra project (Horizon 2020 innovation programme under Grant agreement number: 875527) for funding. References [1] Martha et al., Journal of The Electrochemical Society, 2011, 158 (10) A1115. [2] Jang et al., Journal of Alloys and Compounds, 2014, 612. 51. [3] Liu et al., Journal of Power Sources, 2012, 204, 127

A segmented cell measuring technique for current distribution measurements in batteries, exemplified by the operando investigation of a Zn-air battery

A transimpedance amplifier circuit as well as an instrumental amplifier circuit were used to measure current densities of a zinc-air battery with an integrated segmented current collector foil. Error calculation showed that the transimpedance amplifier is superior to the used instrumental amplifier, but both methods provide valuable and consistent results. They both showed comparable results with operando insight into the current distribution of the battery. The knowledge about those distributions is essential to avoid fast degradation of battery materials and irreversible capacity loss due to heterogeneous dissolution of the anode during discharge. In this work we showed that oxygen starvation as well as gas flow rate leads to large current gradients. It was also demonstrated that heterogeneous current distributions on cathode side induces also a heterogenous dissolution behavior on the anode, resulting in irreversible capacity loss.DL

A segmented cell measuring technique for current distribution measurements in batteries, exemplified by the operando investigation of a Zn-Air battery

A transimpedance amplifier circuit as well as an instrumental amplifier circuit were used to measure current densities of a zinc-air battery with an integrated segmented current collector foil. Error calculation showed that the transimpedance amplifier is superior to the used instrumental amplifier, but both methods provide valuable and consistent results. They both showed comparable results with operando insight into the current distribution of the battery. The knowledge about those distributions is essential to avoid fast degradation of battery materials and irreversible capacity loss due to heterogeneous dissolution of the anode during discharge. In this work we showed that oxygen starvation as well as gas flow rate leads to large current gradients. It was also demonstrated that heterogeneous current distributions on cathode side induces also a heterogenous dissolution behavior on the anode, resulting in irreversible capacity loss

Importance of Time‐Dependent Wetting Behavior of Gas‐Diffusion Electrodes for Reactivity Determination

Tin foil and SnOx/C gas-diffusions electrodes (GDEs) were investigated via electrochemical impedance spectroscopy (EIS) to extract the differential double-layer capacitance (Cdl) as a measure of the wetted surface area. Time-dependent Cdl values revealed an immediate stationary wetting for tin foil electrodes while a distinct increase of Cdl – which becomes stationary with time – was observed for GDEs. The time-dependent wetting behavior of the GDEs was substantiated by physical post-mortem characterization. Since the wetted surface area determines the number of reachable active sites the performance of GDEs should be normalized to the wetted surface area for evaluation of reactivity

Scalable fabrication of multi-layered Cu-based electrodes via solvent-free method for the selective electrochemical conversion of CO2 to C2+ products

In the research field of CO2 electroreduction, gas diffusion electrodes (GDEs) are predominantly manufactured through solvent-based processes. Meanwhile, the solvent-free method has gained heightened attention due to its potential to reduce operational and production expenses, while considering ecological aspects such as solvent evaporation, circulation, and waste treatment. Drawing from its successful applications in other fields, we have specifically developed a solvent-free manufacturing method to produce multi-layered Cu-based GDEs for CO2 electroreduction. The procedure is compatible with industrial production lines, specifically through a roll-to-roll process. By evaluating the interplay between production parameters and electrochemical performance of GDEs via various characterization methods, key factors, i.e., hydrophobicity, gas permeability, thickness, and pore size, were adjusted and applied to achieve a highly selective GDE towards C2+ products (alcohols and ethylene) at industrial relevant currents up to 300 mA cm-2 (ethylene ∼40%, ethanol ∼10%, n-propanol ∼15%).Bundesministerium für Bildung und Forschun