Evaporated manganese films as a starting point for the preparation of thin-layer MnO x water-oxidation anodes

A novel method to prepare anodes for water electrolysis cells has been developed, which starts from layers of elemental manganese deposited by physical vapour deposition (PVD) on indium-doped tin oxide (ITO). Oxidation in dry air at 300 °C transforms this metallic Mn layer into a manganese(II)-rich MnOx coating (x = 1–1.3), which also contains a buried layer of an In–Sn alloy originating from reactions with the ITO support. The MnOx films are well connected to the underlying substrate and act as efficient catalysts for water-oxidation catalysis (WOC) at neutral pH. Detailed post-operando analyses using XRD, SEM, TEM and XAS revealed that the dense MnO/Mn3O4 film is virtually not affected by 2 h of electrochemical WOC at E ≈ +1.8 V vs. RHE, corresponding well to the observed good stability of catalytic currents, which is unusual for such thin layers of a MnOx catalyst. The current densities during electrolyses are so far low (i ≈ 50–100 μA cm−2 at pH 7), but optimization of the preparation process may allow for significant improvements. This new, rather easy, and adaptable preparation method for stable, thin-layer MnOx water-oxidation anodes could thus prove to be very useful for a variety of applications

Direct Measurement of Chemical Distributions in Heterogeneous Coatings

Chemical warfare agents (CWA) can be absorbed by variety of materials including polymeric coatings like paints through bulk liquid contact, thus presenting touch and vapor hazards to interacting personnel. In order for accurate hazard assessments and subsequent decontamination approaches to be designed, it is necessary to characterize the absorption and distribution of highly toxic species, as well as their chemical simulant analogs, in the subsurface of engineered, heterogeneous materials. Using a combination of judicious sample preparation in concert with scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), it should be possible to directly measure the uptake and distribution of CWA simulants in the subsurface of complex multilayer coatings. Polyurethane and alkyd coatings were applied to aluminum and silicon substrates and contaminated with 2-chloroethyl ethyl sulfide (CEES) and dimethyl methylphosphonate (DMMP). The surfaces and cross-sectional interfaces of the contaminated coatings were probed with SEM-EDS to provide imaging, spectral, and elemental mapping data of the contaminant-material systems. This work demonstrated SEM-EDS capability to detect and spatially resolve unique elemental signatures of CWA simulants within military coatings. The visual and quantitative results provided by these direct measurements illustrate contaminant spatial distributions, provide order-of-magnitude approximations for diffusion coefficients, and reveal material characteristics that may impact contaminant transport into complex coating materials. It was found that contaminant uptake was significantly different between the topcoat and primer layers