Herein we report a magnesium powder anode with medium capacity retention and recovery of potential plateaus over reversible cycling. Furthermore powder anodes showed an optimized behavior during charging leading to an improved coulomb efficiency compared to magnesium foil anodes. Battery cells with a powder anode showed pronounced voltage plateaus and no problem to reach a 2.8 V cutoff voltage. Within the compaction pressure range investigated a magnesium powder anode prepared by relatively low pressures showed advantageous properties and was further investigated by electrochemical impedance spectroscopy.

The conversion of CO 2 on tin catalysts via electrolysis leads to valuable chemicals -like CO and formate-and can help to close the carbon cycle. In the current literature catalysts for electrochemical CO 2 reduction reaction (CO 2 RR) are amongst other methods characterized via electrochemical impedance spectroscopy (EIS) in terms of charge transfer resistances neglecting the parallel occurring hydrogen evolution reaction (HER). This may lead to an inapt assignment of the catalyst properties to the CO 2 RR whereas the impedance spectrum displays features of the parasitic HER or mixed information of both reactions. This circumstance is tackled systematically within this work by analyzing linear-sweep voltammograms and impedance spectra under various experimental conditions in order to get more insights into the processes displayed in the respective impedance spectra. The main finding is that the observed high frequency process displays a charge transfer reaction which contains contributions of the HER and CO 2 RR and is not appropriate to evaluate catalysts for the CO 2 RR. This ambiguity was observed for experimental conditions where HER or CO 2 RR prevailed. Additionally, equivalent circuit model simulations confirmed the occurrence of just one arc in the EIS spectrum for parallel occurring charge transfer reactions on the same electrode.

Achieving high current densities in the electrochemical reduction of CO2 is one of the critical issues keeping this technology from commercialization. Although in the past few years, gas diffusion electrode-based electrolyzers have frequently been reported to reach a few hundred milliamperes per square centimeter, higher reaction rates are still endeavored to lower the capital costs and increase the process flexibility necessary for peak-shaving of fluctuating, renewable energies. Here, we report a series of optimizations that allow for the operation of the presented tin oxide nanoparticle-based, homogeneous single-layer gas diffusion electrode at current densities of up to 1.8 A cm–2. Up to this current density, formate faradic efficiency can be kept above 70%. Individual single parameter optimizations, namely, the type of cation contained in the electrolyte, the catalyst loading of the electrode, and the hydrophobicity of the electrode, are investigated separately and afterward combined to achieve a maximized current density.

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