A series of Co1+xFe2–xO4 (0≤x≤2) spinel nanowires was synthesized by nanocasting using SBA‐15 silica as hard template, which was characterized by X‐ray powder diffraction, X‐ray photoelectron spectroscopy, and transmission electron microscopy. The Co1+xFe2–xO4 spinels were applied in the aerobic oxidation of aqueous 2‐propanol solutions to systematically study the influence of exposed Co and Fe cations on the catalytic properties. The activity of the catalysts was found to depend strongly on the Co content, showing an exponential increase of the reaction rate with increasing Co content. Ensembles of Co3+cus (coordinatively unsaturated) sites were identified as the active sites for selective 2‐propanol oxidation, which are assumed to consist of more than six Co ions. In addition, gas‐phase oxidation with and without water vapor co‐feeding was performed to achieve a comparison with liquid‐phase oxidation kinetics. An apparent activation energy of 94 kJ mol−1 was determined for 2‐propanol oxidation over Co3O4 in the liquid phase, which is in good agreement with the gas‐phase oxidation in the presence of water vapor. In contrast to gas‐phase conditions, the catalysts showed high stability and reusability in the aqueous phase with constant conversion in three consecutive runs.

Perovskite oxides are versatile materials due to their wide variety of compositions offering promising catalytic properties, especially in oxidation reactions. In the presented study, LaFe1−xCoxO3 perovskites were synthesized by hydroxycarbonate precursor co-precipitation and thermal decomposition thereof. Precursor and calcined materials were studied by scanning electron microscopy (SEM), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), thermogravimetric analysis (TG), and X-ray powder diffraction (XRD). The calcined catalysts were in addition studied by transmission electron microscopy (TEM) and N2 physisorption. The obtained perovskites were applied as catalysts in transient CO oxidation, and in operando studies of CO oxidation in diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). A pronounced increase in activity was already observed by incorporating 5% cobalt into the structure, which continued, though not linearly, at higher loadings. This could be most likely due to the enhanced redox properties as inferred by H2-temperature programmed reduction (H2-TPR). Catalysts with higher Co contents showing higher activities suffered less from surface deactivation related to carbonate poisoning. Despite the similarity in the crystalline structures upon Co incorporation, we observed a different promotion or suppression of various carbonate-related bands, which could indicate different surface properties of the catalysts, subsequently resulting in the observed non-linear CO oxidation activity trend at higher Co contents.

Due to the variability of the cation occupancy of octahedral and tetrahedral sites, spinel ferrites and cobaltites are particularly interesting to investigate activity trends in oxidation catalysis. Yet, the preparation of the respective catalyst series remains challenging. We employed pulsed laser defect engineering of CoFe2O4 nanoparticles in water to gradually alter the cation occupancy of octahedral and tetrahedral sites by single laser pulses and study its effect on cinnamyl alcohol oxidation. Three CoFe2O4 catalysts from different synthesis methods resembling different initial site occupancy were chosen as starting materials. The laser‐induced randomization of the cation occupancy was verified by Mössbauer spectroscopy and linearly correlated with the conversion of cinnamyl alcohol while the size and Co : Fe ratio was maintained during laser processing. The study solidifies the importance of octahedral Co3+‐sites and the feasibility of pulsed laser processing for altering the cation occupancy and related crystallographic defect density in oxidation catalysis.

Nano-sized perovskites were synthesized in a spray flame from nitrate precursors dissolved in ethanol and in ethanol/2-ethylhexanoic acid (2-EHA) mixtures. Experiments with ethanol led to a broad particle-size distribution and to the formation of undesired phases such as La 2 CoO 4 , La 2 O 3 , and Co 3 O 4. The addition of 2-EHA can initiate micro explosions of the burning droplets and has been systematically investigated toward the formation of single-phase, high-surface-area LaCoO 3 and LaFeO 3 with a narrow size distribution. To investigate the effect of 2-EHA, temperaturedependent changes of the chemical composition of the precursor solutions were analyzed with ATR-FTIR between 23 and 70 C. In all cases, the formation of esters was identified while in the solutions containing iron, additional formation of carboxylates was observed. The synthesized materials were characterized by BET SSA, XRD, SAED and EDX-TEM and their catalytic activity was analyzed, reaching 50% CO conversion at temperatures below 160 and 300 C for LaCoO 3 and LaFeO 3 , respectively.

In a combined experimental and theoretical study we assess the role of Co incorporation on the OER activity of LaCoxFe1−xO3. Phase pure perovskites were synthesized up to x=0.300 in 0.025/0.050 steps. HAADF STEM and EDX analysis points towards FeO2‐terminated (001)‐facets in LaFeO3, in accordance with the stability diagram obtained from density functional theory calculations with a Hubbard U term (DFT+U). Linear sweep voltammetry conducted in a rotating disk electrode setup shows a reduction of the OER overpotential and a nonmonotonic trend with x, with double layer capacitance measurements indicating an intrinsic nature of activity. This is supported by DFT+U results that show reduced overpotentials for both Fe and Co reaction sites with the latter reaching values of 0.32–0.40 V, ∼0.3 V lower than for Fe. This correlates with a stronger reduction of the binding energy difference of the *O and *OH intermediates towards an optimum value of 1.6 eV for x=0.250 , the OH deprotonation being the potential limiting step in most cases. Significant variations of the magnetic moments of both surface and subsurface Co and Fe during OER demonstrate that the beneficial effect is a result of a concerted action involving many surrounding ions, which extends the concept of the active site.