The electrochemical activity of modern Fe–N–C electrocatalysts in alkaline media is on par with that of platinum. For successful application in fuel cells (FCs), however, also high durability and longevity must be demonstrated. Currently, a limited understanding of degradation pathways, especially under operando conditions, hinders the design and synthesis of simultaneously active and stable Fe–N–C electrocatalysts. In this work, using a gas diffusion electrode half-cell coupled with inductively coupled plasma mass spectrometry setup, Fe dissolution is studied under conditions close to those in FCs, that is, with a porous catalyst layer (CL) and at current densities up to −125 mA·cm–2. Varying the rate of the oxygen reduction reaction (ORR), we show a remarkable linear correlation between the Faradaic charge passed through the electrode and the amount of Fe dissolved from the electrode. This finding is rationalized assuming that oxygen reduction and Fe dissolution reactions are interlinked, likely through a common intermediate formed during the Fe redox transitions in Fe species involved in the ORR, such as FeN x C y and Fe3C@N–C. Moreover, such a linear correlation allows the application of a simple metricS-numberto report the material’s stability. Hence, in the current work, a powerful tool for a more applied stability screening of different electrocatalysts is introduced, which allows on the one hand fast performance investigations under more realistic conditions, and on the other hand a more advanced mechanistic understanding of Fe–N–C degradation in CLs.

This work aims to investigate the local structure of mesoporous silica of the type SBA‐15 functionalized with propylphosphonic acid groups by means of an extensive solid‐state NMR spectroscopic study. Here, the functionalized SBA‐15 samples are obtained by a one‐step synthetic method that allowed us better control over the loading and the distribution of the surface functions. In addition to NMR spectroscopy, the materials are characterized by X‐ray diffraction, nitrogen adsorption–desorption and transmission electron microscopy. The 29Si, 13C, 31P and 1H one‐dimensional NMR spectroscopic results are discussed according to the nature of the functional groups in dry and wet materials. This paper proposes a rigorous approach that shows possible hydrogen bonding between adjacent phosphonic acid groups in dry SBA‐15, from the comparative study with an alkylphosphonic acid material. This outcome was demonstrated by two‐dimensional NMR spectroscopic solid–state experiments, including the use of 1H–1H spin‐diffusion exchange experiments, 31P–31P double quanta and an original pulse sequence that corresponds to 31P–1H–1H–31P correlation experiments.

A new nanostructured and highly COOH‐functionalized hybrid organic–inorganic material has been synthesized by the hydrolysis of oligomeric octahedral silsesquioxane (POSS), which contains eight cyanopropyl groups. The hybrid, elemental building block oligomeric octakis(3‐cyanopropyl)silsesquioxane (CN‐POSS) was synthesized from oligomeric octakis(3‐chloropropyl)silsesquioxane (Cl‐POSS) by an exchange reaction. The formation and nanostructuration of the COOH‐functionalized hybrid material were induced by noncovalent hydrogen bonding between COOH‐POSS units without decomposition of the core. The material has been fully characterized by scanning electron microscopy, FTIR and 1H, 13C, and 29Si solid‐state NMR spectroscopy, X‐ray diffraction, and elemental analysis, which confirm that the POSS core remains intact after each chemical modification step. Thermogravimetric analysis indicates that the organic units are thermally stable up to 200 °C. The activation energy related to the proton conductivity of COOH‐POSS has been evaluated and confirms the presence of strong hydrogen bonds. Finally, the accessibility and adsorption capacity of the COOH groups towards transition metal ions have been demonstrated and underline the potential of these hybrid materials in extraction chemistry.

For a successful integration of silicon in high-capacity anodes of Li-ion batteries, its intrinsic capacity decay on cycling due to severe volume swelling should be minimized. In this work, Ni-Sn...

This paper reports on the one‐pot synthesis and characterization of the functionalized mesoporous SBA‐15 silica, which contains two loadings of the different acid groups [CO2H, PO(OH)2 and SO3H]. The thermodynamic features of the water that was confined in these porous silicas was investigated by Differential Scanning Calorimetry (DSC). The results showed that the melting behaviour of the confined water was mainly governed by the pore diameter and, as a consequence, indicated that the chemical “decoration” of the porous surface did not play a key role in the water thermodynamics. On the contrary, the proton conductivity of the hydrated mesoporous materials, which was examined under a wide range of temperatures (–100 to 70 °C), was strongly dependent on both the physical state of the confined water and the acidity of the functional groups that were located at the porous surface. The proton conductivity was shown to be directly related to the pKa and the density of the functional groups attached to the mesopore surface. The high conductivity values that were obtained at a low temperature when the confined water is frozen, led us to postulate that the SO3H‐functionalized SBA‐15 sample could be a promising candidate for electrolyte solid applications in fuel cells.

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Fourier transformed infrared microreflectance spectroscopy is used to probe and compare the consequences of thermal quenching or ionic implantation on the structure of silica. A linear change in the main structural feature associated with Si–O–Si vibration with fictive temperature (Tf) is observed up to Tf=1400 °C. Ionic implantation is shown to shift the frequency of the main IR Si–O–Si vibration toward much lower wavenumbers, for all deposited energies, indicating that a comparison can be drawn between fictive temperature and irradiation effects. Extrapolating the linear changes in the IR structural bands obtained as a function of Tf for the implanted samples, we show that two structural (νTO) and (νB) contributions are not affected by ionic implantation, as they would be by a unique very high Tf. In the case of ionic implantation, we also evidence the development of some specific structural contributions indicating a depolymerization of silica network.