The electrodeposition of noble metals using corresponding dissolved metal salts represents an interesting process for the improvement of the electrocatalytic hydrogen evolution reaction (HER) properties of less active substrate materials. The fact that only a small fraction of the dissolved noble metals reaches the substrate represents a serious obstacle to this common procedure. We therefore chose a different path. It was found that the HER activity of Ni42 alloy drastically increased (η=140 mV at j=10 mA cm⁻²; pH 1) when a platinum counter electrode was used during polarization experiments in acid. This improvement was caused by a platinum transfer from the platinum anode to the steel cathode, a process which occurred simultaneously to the hydrogen evolution. The negligible accumulation of Pt (26 μg) in the electrolyte turns this straight‐forward transfer procedure into a highly cost‐effective, environmentally friendly, and waste reducing approach for the generation of cheap, stable and effective HER electrodes.

A novel oxygen evolution reaction (OER) catalyst (3 D S235‐P steel) based on a steel S235 substrate was successfully prepared by facile one‐step surface modification. The standard carbon‐manganese steel was phosphorized superficially, which led to the formation of a unique 3 D interconnected nanoporous surface with a high specific area that facilitated the electrocatalytically initiated oxygen evolution reaction. The prepared 3 D S235‐P steel exhibited enhanced electrocatalytic OER activities in the alkaline regime, as confirmed by a low overpotential (326 mV at a 10 mA cm⁻²) and a small Tafel slope of 68.7 mV dec⁻¹. Moreover, the catalyst was found to be stable under long‐term usage conditions, functioning as an oxygen‐evolving electrode at pH 13, as evidenced by the sufficient charge‐to‐oxygen conversion rate (faradaic efficiency: 82.11 and 88.34 % at 10 and 5 mA cm⁻², respectively). In addition, it turned out that the chosen surface modification delivered steel S235 as an OER electrocatalyst that was stable under neutral pH conditions. Our investigation revealed that the high catalytic activities likely stemmed from the generated Fe/(Mn) hydroxide/oxohydroxides generated during the OER process. Phosphorization treatment therefore not only is an efficient way to optimize the electrocatalytic performance of standard carbon‐manganese steel but also enables for the development of low‐costing and abundant steels in the field of energy conversion.

For a good reason, water splitting is the most pioneering energy storage technology. However, particularly water electrolysis still has a shadow existence compared to currently used methods for mass production of hydrogen. All known materials currently exploited as anodes for electrocatalytically initiated water-splitting suffer from high overpotentials and substantial mass loss during long term operation in acidic media. Low electrode stability affects operating and maintenance costs and together with high overpotentials directly lowers the overall efficiency of electrocatalytically driven splitting of water. In circumventing these problems, scientists and engineers are currently modifying electrode materials. We chose a completely different path and modified the electrolyte. An electrolysis set up, that consists of a Ni42 stainless steel anode and of hematite which is suspended in high concentration in sulfuric acid and acts as the electrolyte, exhibits oxygen evolution electrocatalysis at extremely low potential (1.26 V vs. RHE; 0.5 M H₂SO₄, j = 30 mA cm⁻²). If implemented in a suitable electrolyzer, an ultralow cell voltage of 1.6 V and an almost quantitative charge to oxygen + hydrogen conversion rate can be achieved. Remarkably, the negligible mass loss of the anode which consists exclusively of non-platinum group metals (non-PGM) during 100 h of operation. Experiments aimed at clarifying the mechanism suggest that Fe₂O₃ is converted to a Fe(II)/Fe(III) oxide species on the cathode which is then reconverted to Fe₂O₃ upon release of molecular oxygen when touching the anode. As a result, the oxygen-evolving centers are likely to be on the oxide particles rather than on the electrode. This proposed mechanism would explain the low potential of the OER electrode (+1.26 V vs. RHE at j = 30 mA cm⁻²) that could not be explained convincingly by an assumed direct oxidation of water molecules.

Giant Keplerate-type molecules with a {Mo₇₂Fe₃₀} core show a number of very interesting properties, making them particularly promising for various applications. So far, only limited data on the electronic structure of these molecules from X-ray spectra and electronic structure calculations have been available. Here we present a combined electronic and magnetic structure study of three Keplerate-type nanospheres—two with a {Mo₇₂Fe₃₀} core and one with a {W₇₂Fe₃₀} core by means of X-ray absorption spectroscopy, X-ray magnetic circular dichroism (XMCD), SQUID magnetometry, and complementary theoretical approaches. Furthermore, we present detailed studies of the Fe³⁺-to-Fe²⁺ photoreduction process, which is induced under soft X-ray radiation in these molecules. We observe that the photoreduction rate greatly depends on the ligand structure surrounding the Fe ions, with negatively charged ligands leading to a dramatically reduced photoreduction rate. This opens the possibility of tailoring such polyoxometalates by X-ray spectroscopic studies and also for potential applications in the field of X-ray induced photochemistry.

A detailed understanding of ultrathin film surface properties is crucial for the proper interpretation of spectroscopic, catalytic, and spin-transport data. We present x-ray magnetic circular dichroism (XMCD) and x-ray resonant magnetic reflectivity (XRMR) measurements on ultrathin ${\mathrm{Fe}}_3{\mathrm{O}}_4$ films to obtain magnetic depth profiles for the three resonant energies corresponding to the different cation species ${\mathrm{Fe}}_{\mathrm{oct}}^{2+}$, ${\mathrm{Fe}}_{\mathrm{tet}}^{3+}$, and ${\mathrm{Fe}}_{\mathrm{oct}}^{3+}$ located on octahedral and tetrahedral sites of the inverse spinel structure of ${\mathrm{Fe}}_3{\mathrm{O}}_4$. By analyzing the XMCD spectrum of ${\mathrm{Fe}}_3{\mathrm{O}}_4$ using multiplet calculations, the resonance energy of each cation species can be isolated. Performing XRMR on these three resonant energies yields magnetic depth profiles that each correspond to one specific cation species. The depth profiles of both kinds of ${\mathrm{Fe}}^{3+}$ cations reveal a $\left(3.9\pm 1.0\right)\text{−}\AA$-thick surface layer of enhanced magnetization, which is likely due to an excess of these ions at the expense of the ${\mathrm{Fe}}_{\mathrm{oct}}^{2+}$ species in the surface region. The magnetically enhanced ${\mathrm{Fe}}_{\mathrm{tet}}^{3+}$ layer is additionally shifted about $2.9\pm 0.4\AA$ farther from the surface than the ${\mathrm{Fe}}_{\mathrm{oct}}^{3+}$ layer.