Monocrystalline, yet porous mosaic platelets of cobalt ferrite, CoFe O , can be synthesized from a layered double hydroxide (LDH) precursor by thermal decomposition. Using an equimolar mixture of Fe , Co , and Fe during co-precipitation, a mixture of LDH, (Fe Co ) Fe (OH) (CO ) ⋅m H O, and the target spinel CoFe O can be obtained in the precursor. During calcination, the remaining Fe fraction of the LDH is oxidized to Fe leading to an overall Co :Fe ratio of 1:2 as required for spinel crystallization. This pre-adjustment of the spinel composition in the LDH precursor suggests a topotactic crystallization of cobalt ferrite and yields phase pure spinel in unusual anisotropic platelet morphology. The preferred topotactic relationship in most particles is [111] ∥[001] . Due to the anion decomposition, holes are formed throughout the quasi monocrystalline platelets. This synthesis approach can be used for different ferrites and the unique microstructure leads to unusual chemical properties as shown by the application of the ex-LDH cobalt ferrite as catalyst in the selective oxidation of 2-propanol. Compared to commercial cobalt ferrite, which mainly catalyzes the oxidative dehydrogenation to acetone, the main reaction over the novel ex-LDH cobalt is dehydration to propene. Moreover, the oxygen evolution reaction (OER) activity of the ex-LDH catalyst was markedly higher compared to the commercial material.

Magnesioferrite (MgFe2O4)‐derived Mesoporous spinels of the type MgFeM3+O4 with M3+=Fe, Al, and Ga obtained upon calcination of hydrotalcite‐like compounds were investigated in the ammonia decomposition reaction at 1 bar and the synthesis of ammonia at 90 bar. The corresponding precursors were synthesized by co‐precipitation at 50 °C and constant pH of 10.5. N2 physisorption, PXRD, HR‐TEM, H2‐TPR, and NH3‐TPD were applied in order to obtain information about the textural, (micro‐)structural, solid‐state kinetics in reducing atmosphere, and adsorption properties of the samples. While phase‐pure layered double hydroxides (LDHs) were obtained for Al and Ga, magnesioferrite as the desired oxide phase and a low fraction of magnetite were formed besides the targeted precursor phase during co‐precipitation in the presence of Fe2+ and Fe3+ species. Reduction of the binary and ternary magnesioferrites occurs via two consecutive reactions. Only the second stage is shifted towards higher temperatures after incorporation of Al and Ga. The latter element boosts the catalytic decomposition of ammonia, yielding a 2‐fold and 5‐fold higher conversion at 500 °C compared to the samples containing Fe3+ and Al3+ species, respectively. In situ XRD measurements showed that this unprecedented promotional effect is related to the generation of (Fe, Ga)Fe3N. This phase, however, is detrimental for the synthesis of ammonia at elevated pressures in which the binary system outperforms the ternary spinels, yielding 30 % of the activity obtained with a highly promoted Fe‐based industrial catalyst.

Mixed cobalt and nickel based layered double hydroxides (LDHs) with Ga as the third cation and the mixed metal oxides (MMOs) resulting from their thermal decomposition were synthesized in various compositions through constant pH coprecipitation and calcination. The structural and textural properties of the catalysts with variable Co/Ni ratios were assessed by N 2 physisorption, powder X-ray diffraction, and electron microscopy. The obtained materials exhibit electrocatalytic activity for the oxygen evolution reaction in alkaline solution. The highest activity was found for catalysts containing both transition-metal cations, Co and Ni. However, comparison of the LDH precursors and the calcined MMOs revealed a composition-dependent effect of calcination. Co-rich LDH tends to lose activity when calcined, whereas Ni-rich LDH gains activity. The optimal cation composition of the LDH was Co 1.5 Ni 0.5 Ga with an overpotential of 382 mV. The highest performance among the MMOs, on the other hand, has been encountered for the Co 0.5 Ni 1.5 Ga composition, reaching a similar overpotential.

Numerous catalysts have been reported with enhanced performance, e.g. longer lifetime and improved selectivity, for the electrochemical CO2 reduction reaction (CO2RR). Respectively little is, however, known about the influence of the electrode structuring and pre-treatment on this reaction for catalytic layers. Thus, we herein report on the modification of the catalyst environment of a Cu-ZnO-carbon black catalyst by variation of the ink composition and subsequent electrode treatment before performing CO2RR. We furthermore provide insight into the impact of solvents used for the ink preparation, ionomer and additives like pore forming agents as well as post treatment steps in terms of pressing and sintering of electrodes on the CO2RR performance. Although using the same catalyst for all electrodes, remarkable differences in hydrophobicity, surface morphology and electrochemical performance with respect to stability and product distribution are observed. Our study reveals the critical role of the catalytic layer assembly aside using proper catalysts. We furthermore show that the parasitic hydrogen formation and flooding behavior can be lowered and C2+ product formation enhanced when operated in optimized gas diffusion electrodes (GDE).