Yes, we CAN: Partial oxidation of inactive MnO nanoparticles by CeIV as oxidant gives active MnOx catalysts that are suitable for effective photochemical and electrochemical water oxidation. The active MnOx catalyst contains mixed‐valent MnII, MnIII, and MnIV species (see picture; green and violet) interconnected through oxido bridges (red) with defects and disorders. MnOx is analogous to calcium–manganese oxide systems where the calcium sites are replaced by MnII or MnIII ions.

Splitting of water to hydrogen and oxygen on colloidal catalysts is a promising method for future energy and chemistry cycles. The currently used high-performance oxides containing expensive elements (Ru, Ir) are progressively being replaced by more sustainable ones, such as Co3O4. Although the size of the nanoparticles determines their catalytic performance, the control over the particles’ diameter is often synthetically difficult to achieve. An additional obstacle is the presence of stabilizing agent, an organic molecule that blocks accessible surface-active centers. Herein, we present how precise control over size of the cobalt oxide nanoparticles (Co3O4 NPs), their colloidal stability, and the ligand-free surface affect overall performance of the photocatalytic oxygen evolution. We accordingly correlated the photochemical results with the electrochemical studies, concluding that accessibility of the active species on the particles’ surface is crucial parameter in water oxidation.

Sophisticated IrO2(110)-based model electrodes are prepared by deposition of a 10 nm thick single-crystalline IrO2(110) layer supported on a structure directing RuO2(110)/Ru(0001) template, exposing a regular array of mesoscopic roof-like structures. With this model electrode together with the dedicated in-situ synchrotron based techniques (SXRD, XRR) and ex-situ characterization techniques (SEM, ToF-SIMS, XPS) the corrosion process of IrO2(110) in acidic environment is studied on different length scales. Potential-induced pitting corrosion starts at 1.48 V vs. SHE and is initiated at so-called surface grain boundaries, where three rotational domains of IrO2(110) meet. The most surprising results is, however, that even when increasing the electrode potential to 1.94 V vs. SHE still 60-70 % of the IrO2 film stays intact down to the mesoscale and atomic scale and no uniform thinning of the IrO2(110) layer is encountered. Neither flat IrO2(110) terraces nor single steps or grain boundaries, where only two rotational domains meet, are attacked. Ultrathin single-crystalline IrO2(110) layers seem to be much more stable in the anodic corrosion than hitherto expected.

Nickel-manganese oxides with variable Ni : Mn ratios, synthesised from heterobimetallic single-source precursors, turned out to be efficient water oxidation catalysts. They were subjected to oxidant-driven, photo- and electro-catalytic water oxidation showing superior activity and remarkable stability. In addition, a structure-activity relation could be established.

In regard to earth-abundant cobalt water oxidation catalysts, very recent findings show the reorganization of the materials to amorphous active phases under catalytic conditions. To further understand this concept, a unique cobalt-substituted crystalline zinc oxide (Co:ZnO) precatalyst has been synthesized by low-temperature solvolysis of molecular heterobimetallic Co(4-x)Zn(x) O4 (x = 1-3) precursors in benzylamine. Its electrophoretic deposition onto fluorinated tin oxide electrodes leads after oxidative conditioning to an amorphous self-supported water-oxidation electrocatalyst, which was observed by HR-TEM on FIB lamellas of the EPD layers. The Co-rich hydroxide-oxidic electrocatalyst performs at very low overpotentials (512 mV at pH 7; 330 mV at pH 12), while chronoamperometry shows a stable catalytic current over several hours.

The synthesis of monodisperse, surfactant‐free, Ni‐substituted ZnO nanocrystallites (ZnO:Ni) by the mild solvolysis of heterobimetallic Ni4−xZnxO4 cubane‐like precursors (x=1–3) in benzylamine is reported. Ni4−xZnxO4 was grafted by electrophoretic deposition onto fluorine‐doped tin oxide glass substrates and used as an active and stable working electrode for water oxidation. Upon the application of a voltage at the electrodes, the ZnO:Ni precatalyst leads to an active composite material that can oxidize water (>15 h) with an increasing catalytic current. In contrast, the performance of homometallic NiO reference materials decreases rapidly over time and is surpassed by the composite from the ZnO:Ni precatalyst in terms of both stability and activity. Extensive characterization of the as‐prepared and activated ZnO:Ni precatalyst by using hard X‐ray photoelectron spectroscopy revealed that the excellent performance of the electrode material is because of the formation of a unique self‐supported turbostratically disordered mixture of γ‐NiOOH/α‐Ni(OH)2‐like phases from the rapid dissolution of ZnII in the ZnO:Ni precatalyst into the electrolyte during activation.

A detailed study of the near-surface structure and composition of Nb, the material of choice for superconducting radio-frequency accelerator (SRF) cavities, is of great importance in order to understand the effects of different treatments applied during cavity production. By means of surface-sensitive techniques such as grazing incidence diffuse x-ray scattering, x-ray reflectivity, and x-ray photoelectron spectroscopy, single-crystalline Nb(100) samples were investigated in and ex situ during annealing in an ultrahigh vacuum as well as in nitrogen atmospheres with temperatures and pressures similar to the ones employed in real Nb cavity treatments. Annealing of Nb specimens up to 800°C in a vacuum promotes a partial reduction of the natural surface oxides (Nb 2 O 5 , NbO 2 , and NbO) into NbO. Upon cooling to 120°C, no evidence of nitrogen-rich layers was detected after nitrogen exposure times of up to 48 h. An oxygen enrichment below the Nb-oxide interface and posterior diffusion of oxygen species towards the Nb matrix, along with a partial reduction of the natural surface oxides, was observed upon a stepwise annealing up to 250°C. Nitrogen introduction to the system at 250°C promotes neither N diffusion into the Nb matrix nor the formation of new surface layers. Upon further heating to 500°C in a nitrogen atmosphere, the growth of a new subsurface Nb x N y layer was detected. These results shed light on the composition of the near-surface region of Nb after low-temperature nitrogen treatments, which are reported to lead to a performance enhancement of SRF cavities.

With in-situ surface X-ray diffraction (SXRD) and X-ray reflectivity (XRR) in combination with ex-situ characterization by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV) the electrochemical reduction of an ultrathin (1.66 nm thick) single crystalline RuO2(110) layer supported of Ru(0001) was studied in acidic environment, providing clear-cut evidence and mechanistic details for the transformation of RuO2 towards hydrous RuO2 and metallic Ru. The reduction process proceeds via proton insertion into the RuO2(110) lattice. For electrode potentials (0 to-50mV vs. SHE) the layer spacing of RuO2(110) increased, maintaining the octahedral coordination of Ru (SXRD). Continuing proton insertion at-100 to-150 mV leads to transformation of lattice oxygen of RuO2 to OH and water that destroys the connectivity among the Ru octahedrons and eventually to the loss of crystallinity (SXRD) in the RuO2(110) film at-200 mV accompanied by a swelling of the layer with well-defined thickness (XRR). During the protonation process soluble Rucomplexes may form. XPS provide evidence for the transformation of RuO2(110) to a hydrous RuO2 layer, a process that proceeds first homogenously and at higher cathodic potentials heterogeneously by re-deposition of a previously dissolved Ru complexes.