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Nanometre‑thin, free‑flowing liquid sheets now let Swiss Light Source users record pristine VUV absorption spectra of water, and soon any solvent.

Energy storage technologies with long storage duration are essential to stabilize electricity grids with a high share of intermittent renewable power. In a redox flow battery, the electrochemical conversion unit, where the charging and discharging reaction takes place, is spatially separated from the energy storage medium. In the all-vanadium redox flow battery (VRFB), a sulfuric acid aqueous electrolyte with dissolved vanadium ions is used as the storage medium. Vanadium is present in 4 different oxidation states, the redox couple vanadium(II) and (III) on the negative side of the cell, and vanadium(IV) and (V) on the positive side. This allows the battery to be repeatedly charged and discharged. A separator or membrane is used between the negative and positive electrode, which should selectively conduct the ions of the supporting electrolyte and minimize the passage of vanadium ions. Fluorinated membranes, such as Nafion™, are often used for this key component, but these ionomers were not originally developed for this application and therefore have functional shortcomings. Furthermore, the production and use of fluorinated materials is to be severely restricted or even banned in Europe. Therefore, the development of hydrocarbon-based membranes for the VRFB is of great importance. The study reported here focuses on polybenzimidazole polymers and membranes, which could be a promising materials class for next generation flow batteries. 

Employing a bipolar ion conducting membrane (BPM) in forward bias is a convenient solution for the biggest issues in the more common anion exchange membrane (AEM) CO2 co-electrolysis: the degradation of the performance caused by carbonate salt precipitation at the cathode and the decrease of net CO2 conversion caused by the crossover of this molecule from cathode to anode also requiring energy for downstream gas separation. However, the performance and stability of this device remain largely insufficient when using such a BPM configuration. To understand the reasons for this, we performed time-resolved X-ray tomographic microscopy of an operating BPM CO2 electrolyzer. The imaging method reveals partly unexpected degradation processes that result in design recommendations for improvement.

CeO₂ significantly enhances the oxygen evolution reaction (OER) activity of CoOx, although the mechanism behind this synergy is still unclear. Here, operando hard X-ray absorption spectroscopy (hXAS) is applied to monitor the Co-K edge and Ce L3 edge in CoOx/CeO2 to shed light on the evolution of Co and Ce oxidation states during OER. In addition, ex situ soft XAS (sXAS) characterizations provide information on the irreversible surface-specific transformations of the Co L3 edge as well as the O K edge.

The complex nature of liquid water saturation in polymer electrolyte fuel cell (PEFC) catalyst layers (CLs) greatly affects the device performance. To investigate this problem, a method to quantify the presence of liquid water in a PEFC CL using small-angle X-ray scattering (SAXS) was developed in a collaboration of researchers of the Federal Institute for Materials Research and Testing (BAM, Berlin, Germany), the Photon Science Division and the Electrochemistry Laboratory of PSI. The method leverages the differences in electron densities between the solid catalyst matrix and the CL-pores filled with liquid water under dry and wet conditions, respectively.

We report an in-depth investigation of the local atomic geometry, electronic and crystallographic structure evolution of nano-sized LiMn₂O₄ using operando XAS and XRD to shed light on (de-)lithiation mechanism when cycled in wide voltage range of 2.0 to 4.3 V vs Li⁺/Li. Leveraging on these findings, a novel electrochemical cycling protocol, with periodic deep discharge, yields superior electrochemical performance cycled in the range of 3.3 to 4.3 V exhibiting an excellent structure cyclability and an unprecedented increase in the specific capacity upon long cycling.

Electrochemical energy conversion devices, such as fuel cells and electrolyzers, using an anion exchange membrane (AEM) operating in the alkaline regime offer the prospect of the use of non-noble metal electrocatalysts and lower-cost cell construction materials. The wide-spread application of electrochemical cells with AEMs has been largely limited by the low chemical stability of the material. AEM degradation is triggered by i) nucleophilic attack by OH⁻, and ii) by reaction with free radicals formed during cell operation. Whereas the alkaline stability of AEMs has been greatly increased over the last 10 years, the understanding of mechanisms of radical induced degradation is limited. In this study, we have addressed this topic for the first time.

Our findings disclose that P-functionalization successfully enhances the oxygen evolution reaction (OER) activity of different cobalt-based catalysts (namely, La_0.2Sr_0.8CoO_3–δ, La_0.2Sr_0.8Co_0.8Fe_0.2O_3–δ, and CoO_x) at near-neutral pHs and that both phosphate ion assistance in the OER mechanism and catalyst Co oxidation state can play a role in the enhanced OER activity.

The mass loading of Si-graphite electrodes is often considered as a parameter of secondary importance when testing their performance. However, if a sacrificial additive is present in the electrolyte, the electrode loading becomes the battery cycle-life-determining factor. A lower loading was obtained by keeping slurry preparation steps unchanged from binder to binder and resulted in a longer lifetime for some of the binders. When the final loading was kept constant instead, the performance became independent of the binder used.