Joerg J. Schneider

In Nickel ferrites a low oxygen reduction activity and poor stability represent a drawback in rechargeable zinc‐air battery technology. This contribution presents a strategy using self‐templating for fabricating a nanohybrid material composed of NiFe ₂ O ₄ nanocubes encapsulated in N, P‐doped carbon nanohorns (CNH). Benefiting from the efficient mass and electron transfer of such N, P‐doping, CNH provide a significant number of active sites preventing aggregation and dissolution of active ferrite components in the composite. Thus, the NiFe ₂ O ₄ @CNH‐N‐P nanohybrid catalyst exhibits a high half‐wave potential (0.79 V) and a low Tafel slope of 56.5 mV/dec, following a four‐electron pathway for oxygen reduction (ORR). The NiFe ₂ O ₄ @CNH‐N‐P nanohybrid catalyst work in full‐cell zinc air battery configuration as bifunctional cathode catalyst in conjunction with a ZnO/C composite anode. The maximum power density derived from polarization curves for ZAB based on NiFe ₂ O ₄ @CNH‐N‐P is 54 mW/cm ² and thus exceeds a benchmark catalyst composed of 20% Pt/C+RuO ₂ of 28 by 26 mW/cm ² . The assembled secondary ZAB can be cycled for more than 300 h in a galvanostatic charge–discharge test. This work provides insight into the rational composition and morphology design, as well as full materials and electrochemical characterization, of an earth‐abundant electrocatalyst with efficient electrocatalytic activity.

Herein, we investigate how aliovalent doping and application of an external electrical field modulates the catalytic activity of nanoscale ceria ( n CeO ₂ ) towards CO oxidation. Gd ³⁺ and La ³⁺ were doped into the n CeO ₂ lattice. Such doping influences the concentration and mobility of oxygen vacancies, which are promoting CO oxidation to CO ₂ . When applying an electric potential, charge transport within n CeO ₂ is modulated. Our results show that both dopants Gd ³⁺ and La ³⁺ lead to an increasing V _O concentration, whereas the impact of the applied potential on the oxidation behaviour varies with catalyst composition. The applied electric potential markedly improves the activity of undoped n CeO ₂ and 5% Gd ³⁺ -doped n CeO ₂ ; however, it causes no significant change in CO oxidation capability in 2.5% Gd ³⁺ -doped and La ³⁺ -doped samples. These findings can be understood considering the applied potential and its influence on the polaron mobility and V _O arrangement, which are controlled by the underlying oxidic defect structure.

An analytical reference point for the Butler–Volmer equation is derived introducing the golden ratio φ . It allows to estimate the exchange current density for reversible electrochemical processes with low overpotential and symmetric charge transfer.

Synthesis and characterization of iron and nickel metal complexes employing the monodentate N-heterocyclic silylene RSiPh (R = PhC(N^tBu)₂) is reported. The iron complexes were obtained by reacting the 20 valence electron bis(η⁶-toluene)iron sandwich generated in situ by co-condensation of elemental iron and toluene vapor with the silylene ligand. The corresponding nickel complexes are accessible by employing bis(1,5-cyclooctadiene)nickel(0) as a zerovalent nickel source. The N-heterocyclic silylene RSiPh (R = PhC(N^tBu)₂) ligand was tethered in the periphery of bis(benzene)chromium, resulting in the formation of a unique bidentate organometallic pincer ligand with two independent silylene units bridged by a bis-benzene moiety. All complexes were fully characterized by multinuclear NMR spectroscopy, IR spectroscopy, mass spectrometry and a single-crystal X-ray analysis of one of the iron compounds. The results underscore the versatility of silylenes and demonstrate the utility of highly reactive bis(η⁶-toluene)iron as a single-step approach to zerovalent Fe-silylene complexes.

Zirconium and hafnium doped indium tin oxide (ITO) thin films are fabricated via atomic layer deposition (ALD) at 200°C from trimethylindium, tetrakis(dimethylamido)tin, tetrakis(dimethylamido)zirconium, and tetrakis(diethylamido)hafnium, using water as oxidant. Grazing incidence X‐ray total scattering employing synchrotron radiation reveals a highly disordered structure with a short‐range order, exhibiting correlation lengths of up to ∼13 Å. This is also reflected in high‐resolution transmission electron microscopy, revealing an amorphous intermixed state of all constituting components. Increasing amounts of fully coordinated oxygen species with increasing amounts of dopant are evidenced by X‐ray photoelectron spectroscopy analysis and attributed to zirconium and hafnium's ability to form strong oxygen bonds, and thereby suppressing the formation of oxygen vacancies. The Zr‐ and Hf‐doped ITO thin films are integrated into thin‐film transistor (TFT) devices to evaluate their suitability as semiconducting material. The electrical measurements reveal saturation mobilities ( µ _{s at} ) of 1.92–9.81 cm ² V ⁻¹  s ⁻¹ , with high current on/off ratios ( I _On /I _Off ) of 10 ⁶ –10 ⁸ . This study demonstrates the subtle influence of small amounts of Zr and Hf on TFT performance. This proves the ability to control the electrical behavior of TFT devices by controlled incorporation of dopants like Zr and Hf into their active channel layer.

Porous ordered alumina (PAOX) is described by using elements of hydrodynamic and quantum mechanical theory. It is shown that the collective pore arrangement can be described by analogs to eigenenergies, Hamilton operators or the Pauli principle.

Microscopic carbon/SiO ₂ composites are composed of a huge number of interfacial contacts. When those are exposed to moderate ohmic fields gas adsorptivity of the composite is modulated. Herein it shows that it is possible to manipulate, modify, and follow gas adsorption selectivity by in situ spectroscopy under electrical charging. In a model gas mixture of CO ₂ and N ₂ , for the first time it can be shown that a change in gas composition is observed and can be controlled locally above an electrically charged carbon/SiO ₂ surface using in situ Raman spectroscopy. The technique is implemented in an ongoing non‐stationary adsorption process using the advantage of the fast on‐off switchability of the electric field as compared to the typically slow equilibration kinetics of adsorption on activated carbon. An increase in gas phase concentration of 3.5% and 5.5% of CO _2, which is equivalent to a change in selectivity of 11% and 24% of CO ₂ over N _2, just by applying an electrical input power of 0.53 and 1.12 W is achieved and quantified by Raman spectroscopy, respectively. The method bears general potential for mixtures of gases with different responses to the electric field, as well as for processes where a local manipulation of gas concentrations is necessary.

Homoleptic isonitrile compounds of Fe, Co and Ni are accessible by a direct route employing metal atoms and isonitrile ligands. Our approach is of general utility for synthesizing homoleptic metal complexes under extremely mild chimie douce conditions.

Influencing the adsorptive processes of gases by external stimuli is an ongoing research task of academic and technological relevance. Technologically external stimuli like pressure, vacuum, temperature, magnetic field, or electrical phenomena are the most common ones with which adsorptive and desorptive processes can be influenced. In the case of pure electric field swing adsorption (EFSA) of solid/gas mixtures, however, experimental knowledge concerning carbon materials is lacking so far. A new approach to the electrical field effect on gas adsorption and desorption is presented. Ar, N ₂ and CO ₂ interact with an all‐solid composite material composed of activated porous carbon and silica characterized by a high amount of charged interfaces under isothermal conditions and ambient temperature. The intimate contact of both components in the composite allows for the formation of multiple resistor‐conductor interfaces enabling the reversible physisorption of these gases using electric fields in the lower V and mA range. The adsorptive/desorptive swing effect depends on the polarizabilities of the gases in particular their dipoles and to an even larger extent on the field induced quadrupole moments of the probe gases Ar, N ₂ and CO ₂ .

Thin semiconducting films of magnesium doped indium‐ and tin oxide are prepared by thermal atomic layer deposition (ALD). The metal oxide films are deposited at 200 °C from the precursors trimethylindium, tetrakis(dimethylamido)tin, bis(ethylcyclopentadienyl)magnesium and water as oxidant. These thin‐films are observed to be amorphous by electron microscopy and X‐ray diffraction. However, they exhibited a near‐range atomic order with correlation lengths of up to 10 Å, as demonstrated by high energy total scattering at grazing incidence employing synchrotron radiation. Even minor alterations in composition reveal a significant impact on the thin‐film transistor (TFT) device parameters, due to magnesium's high oxygen binding capability and its ability to inhibit the formation of oxygen vacancies, resulting in a decrease of free charge carriers in the material. Stability tests indicate a device degradation after storage in ambient conditions due to water adsorption on the surface, which could be reversed by an additional annealing step which qualify the films as robust. This studie demonstrate the possibility of employing minor amounts of high band gap oxides such as MgO to manipulate and control the electric behavior of the active channel layer performance in inorganic TFT devices.