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Within the Recycalyse project different research organization and industrial partners worked together to develop catalysts for the oxygen evolution reaction for proton exchange membrane electrolysis that reduce the use of critical raw materials. The catalysts are applied to polymer electrolyte membranes via a direct coating process and tested both in single cells and at stack level. In order to reduce the dependence on material imports in Europe in the long term, recycling is considered for the catalysts, electrodes and the entire system. [ABSTRACT FROM AUTHOR]

Porous carbon‐based electrodes are frequently applied in electrochemical energy technologies, for instance in fuel cells and redox flow batteries. In previous work, we observed that the final structure of a fuel cell electrode is dominated by both the morphology of the support material and its processing into a 3D porous structure. Herein, the impact of catalyst support morphology on the performance of polymer electrolyte membrane fuel cells was studied comparing carbon‐supported platinum catalysts only differing in the shape of the carbon support material with otherwise similar features. Carbon‐supported Pt catalysts were obtained by carbonization of polyaniline (PANI) in long fibrous, short fibrous, and granular shape. The chemical identity of the PANI precursors was demonstrated by FTIR spectroscopy and elemental analysis (EA). The final carbon‐supported platinum catalysts were characterized by EA, Raman spectroscopy, XRD, and TEM exhibiting similar degree of carbonization, nanoparticle size, and nanoparticle dispersion. The effect of support morphology and the resulting differences in the 3D structure of the porous electrode were investigated by focused ion beam‐scanning electron microscopy slice and view technique and correlated to their fuel cell performance. [ABSTRACT FROM AUTHOR]

The polymer electrolyte membrane (PEM) water electrolysis is a promising technology for the production of hydrogen from water using fluctuating renewable electricity sources. However, the investment cost of the PEM electrolysis technology has to be lowered considerably to achieve a widespread application. Polymer materials can be used as low‐cost materials to solve this issue. However, the conditions within the electrolysis cells are challenging for polymeric materials, especially for materials used within the oxygen‐evolving electrode. This study reports the new concept of electronically and protonic conductive polymer structures for the PEM water electrolysis produced by additive manufacturing and first results of investigations on compounds suitable for this concept. [ABSTRACT FROM AUTHOR]

In this work Pt@TiO2 nanocomposite electrocatalysts for methanol oxidation were synthesized using a one-pot process by hydrophobic nanoreactor templating. TiO2 was used as a support material for the platinum nanoparticles, thereby providing strong metal–support interactions. The Pt@TiO2 electrocatalyst consists of a monolayer of spherical superstructures comprising finely dispersed platinum nanoparticles in a crystalline TiO2 matrix as revealed by high resolution (scanning) transmission electron microscopy (HR-TEM and HR-STEM) combined with energy dispersive X-ray spectroscopy (EDX), electron diffraction and X-ray photoelectron spectroscopy (XPS). The Pt@TiO2 electrocatalyst showed high methanol oxidation activity, exceeding the activity of a commercial Pt/C catalyst by a factor of 2.5, as well as a cathodically shifted methanol oxidation peak. The increased methanol oxidation activity of Pt@TiO2 was attributed to its enhanced CO oxidation ability, an undesired intermediate, which is formed during methanol oxidation and poisons the Pt-surface. Indeed, CO stripping experiments confirmed that CO oxidation takes place at lower potentials in the case of Pt@TiO2, leading to a cathodic shift of the CO oxidation peak by 100 mV compared to a commercial Pt/C reference catalyst. Insights into the mechanism of methanol oxidation on Pt@TiO2 were found by comparison of methanol oxidation in different electrolytes. It was found that methanol oxidation via the CO-route is more pronounced on Pt@TiO2 than on Pt/C. The improved activity for CO oxidation resulted thereby in a better catalyst performance, especially at low potentials, and an increased stability, as demonstrated by chronoamperometry. The long-term stability of the catalyst was further addressed by accelerated stress tests (AST), which showed that the superior catalytic activity is retained even after 30 000 potential cycles. [ABSTRACT FROM AUTHOR]

Abstract: A facile approach for the template‐free synthesis of highly active non‐noble metal based oxygen reduction reaction (ORR) electrocatalysts is presented. Porous Fe−N−C/Fe/Fe3C composite materials are obtained by pyrolysis of defined precursor mixtures of polyformamidine (PFA) and FeCl3 as nitrogen‐rich carbon and iron sources, respectively. Selection of pyrolysis temperature (700–1100 °C) and FeCl3 loading (5–30 wt%) yields materials with differing surface areas, porosity, graphitization degree, nitrogen and iron content, as well as ORR activity. While the ORR activity of Fe‐free materials is limited (i.e., synthesized from pure PFA), a huge increase in activity is observed for catalysts containing Fe, revealing the participation of the metal dopant in the construction of active electrocatalytic sites. Further activity improvement is achieved via acid‐leaching and repeated pyrolysis, a result which is attributed to the creation of new active sites located at the surface of the porous nitrogen‐doped carbon by dissolution of the Fe and Fe3C nanophases. The best performing catalyst, which was synthesized with a low Fe loading (i.e., 5 wt%) and at a pyrolysis temperature of 900 °C, exhibits high activity, excellent H2O selectivity, extended stability, in both basic and acidic media as well as a remarkable tolerance toward methanol. [ABSTRACT FROM AUTHOR]

Electrochemical degradation (ED) of carbon felt electrodes was investigated by cycling of a flow through all-vanadium redox flow battery (VRFB) and conducting half-cell measurements with two reference electrodes inside the test bench. ED was detected using half-cell and full-cell electrochemical impedance spectroscopy (EIS) at different states of charge (SOC). Reversing the polarity of the battery to recover cell performance was performed with little success. Renewing the electrolyte after a certain amount of cycles restored the capacity of the battery. X-ray photoelectron spectroscopy (XPS) reveals that the amount of surface functional increases by more than a factor of 3 for the negative side as well as for the positive side. Scanning electron microscope (SEM) images show a peeling of the fiber surface after cycling the felts, which leads to a loss of electrochemically active surface area (ECSA). Long term cycling shows that ED has a stronger impact on the negative half-cell [V(II)/V(III)] than the positive half-cell [V(IV)/V(V)] and that the negative half-cell is the rate-determining half-cell for the VRFB. [ABSTRACT FROM AUTHOR]

The degradation of LiNi 0.8 Co 0.15 Al 0.05 O 2 (LNCAO), a cathode material in lithium-ion-batteries, was studied using in situ powder diffraction and in situ Ni K edge X-ray absorption spectroscopy (XAS). The fatigued material was taken from a 7 Ah battery which was cycled for 34 weeks under defined durability conditions. Meanwhile, a cell was stored, as reference, under controlled conditions without electrochemical treatment. The fatigued LNCAO used in this study showed a capacity loss of 26% ± 9% compared to the non-cycled material. During charge and discharge the local and the overall structure of LNCAO was investigated by X-ray near edge structure (XANES) analysis, the extended X-ray absorption fine structure (EXAFS) analysis and by using Rietveld refinement of in situ powder diffraction patterns. Both powder diffraction and XAS revealed additional, rhombohedral phases which do not change with electrochemical cycling. Moreover, a phase with the lattice parameters of fully lithiated LNCAO was still present in the fatigued material at high potentials, while it was absent in the non-fatigued reference material. The coexistence of these phases is described by domains within the LNCAO particles, in correlation with the observed fatigue. [ABSTRACT FROM AUTHOR]