Integration of noble metals into semiconductor‐based nanoparticle gel structures facilitates the extraction of photoexcited charge carriers upon illumination. While charge carrier generation takes place in the semiconductor component, noble metals in contact to the semiconductor act as electron sinks. Thus, the nature of the interface between the components is of essential importance, as it dictates the characteristics of the interparticle contact. Here, the influence of the nanoscale building block design on the charge carrier dynamics in cryoaerogels consisting of CdSe/CdS nanorods and nanoplatelets as well as of gold or platinum is reported. It is shown that direct growth of noble metal domains onto the semiconductor prior to the gelation significantly facilitates charge carrier separation in their cryoaerogel structures compared to gels from the colloidal mixtures of semiconductor and noble metal nanoparticles, the latter ones having less defined metal/semiconductor boundaries and much more arbitrary component distributions. Although the structure of the different cryoaerogel systems is similar at the micro‐ and macroscale, nanoscale differences caused by the two synthetic routes drive essentially different behavior regarding the charge carrier dynamics efficiency. These effects are observed spectroelectrochemically via intensity‐modulated photocurrent spectroscopy emphasizing the importance of the semiconductor–metal connection in the hybrid structures.

The transformation towards a circular economy based on sustainable technologies requires future-oriented materials development, which considers materials recycling with a minimum environmental impact (EI). This demands a holistic approach towards materials design, including a combined assessment of functional and environmental performance. Scientific methods for environmental assessment, e.g., life cycle assessment (LCA), are well established but rarely integrated into the chemical process development at early stages. Consequently, sustainability claims often lack scientific verification. Here, we test the approach of integrating a screening LCA into the development of a chemical (recycling) process. As a relevant use case, we selected the recently developed oxygen transport membrane (OTM) material (La_0.9Ca_0.1)₂Ni_0.75Cu_0.25O_4±δ (LCNC). An initial LCA identified the consumption of primary metal nitrates as a major contributor to the EI of the primary synthesis. To address this issue, a Pechini-based chemical recycling process for LCNC was developed, which involves microwave-heated dissolution and subsequent re-gelation. Experimental results demonstrate the synthesis of recycled LCNC powder with primary-like properties, similar reaction behaviour, and > 96 % yield. Based on the LCA results, the EI of recycling is reduced by up to 76 % compared to the primary synthesis in 12 of 14 impact categories. Measures for the simultaneous improvement of the process functionality and environmental performance were identified. The approach of integrating LCA in chemical process development is discussed critically based on the given use case. The results strongly encourage the integration of LCA as a standard method into the future development of sustainable chemical processes.

La₂NiO_4+δ particles with a plate-like morphology were prepared from a NaOH melt by molten-flux synthesis. For this purpose, the intermediates from a sol–gel process were used as reactants. Using powder X-ray diffraction, the sol–gel intermediates were identified as a mixture of tetragonal La₂O₂CO₃ and cubic NiO. The existence of NiO was also confirmed by transmission electron microscopy in combination with electron-energy loss spectroscopy. The ultrafine mixed sol–gel intermediates were then mixed with NaOH powder and additional water in a nickel crucible and heated to 673 K for 8 h. The chemical reactions in the air during the molten-flux synthesis and the influence of the salt on the formation of La₂NiO_4+δ were examined by thermogravimetric analysis. The powder X-ray diffraction indicated a K₂NiF₄-type tetragonal structure with the I4/mmm space group for the reaction product. The scanning electron microscopy showed plate-like La₂NiO_4+δ crystals with a length and thickness of approximately 9 µm and 2 µm, respectively, while the energy-dispersive X-ray spectroscopy revealed a homogeneous distribution of lanthanum and nickel in the product powder. The influence of the processing parameters on the product generation, as well as on the size and morphology of the La₂NiO_4+δ particles, was systematically studied.

La_0.6Ca_0.4Co_1–xFe_xO_3–d in its various compositions has proven to be an excellent CO₂-resistant oxygen transport membrane that can be used in plasma-assisted CO₂ conversion. With the goal of incorporating green hydrogen into the CO₂ conversion process, this work takes a step further by investigating the compatibility of La_0.6Ca_0.4Co_1–xFe_xO_3–d membranes with hydrogen fed into the plasma. This will enable plasma-assisted conversion of the carbon monoxide produced in the CO₂ reduction process into green fuels, like methanol. This requires the La_0.6Ca_0.4Co_1–xFe_xO_3–d membranes to be tolerant towards reducing conditions of hydrogen_. The hydrogen tolerance of La_0.6Ca_0.4Co_1–xFe_xO_3–d (x = 0.8) was studied in detail. A faster and resource-efficient route based on ultrasonic spray synthesis was developed to synthesise the La_0.6Ca_0.4Co_0.2Fe_0.8O_3–d membranes. The La_0.6Ca_0.4Co_0.2Fe_0.8O_3–d membrane developed using ultrasonic spray synthesis showed similar performance in terms of its oxygen permeation when compared with the ones synthesised with conventional techniques, such as co-precipitation, sol–gel, etc., despite using 30% less cobalt.

Sodium cobaltite (Na _x CoO ₂ ) is one of the most renowned and thermoelectrically promising p ‐type cobalt oxide materials, showing exceptional performance in this domain. Nonetheless, its thermal instability in air renders it unsuitable for high‐temperature applications such as energy harvesting from industrial waste heat. To utilize the beneficial properties of Na _x CoO ₂ , microscale Na _x CoO ₂ template particles of significantly larger size were effectively embedded within a thermally stable Ca ₃ Co _{4− y} O _{9+ δ} –Na _x CoO ₂ –Bi ₂ Ca ₂ Co ₂ O ₉ triple‐phase matrix. This approach additionally aimed to enhance the texture and boost the thermoelectric performance of the ceramic composite. Highly textured p ‐type ceramic composites were fabricated via uniaxial cold‐pressing and pressureless sintering in air. The unique hexagonal Na _x CoO ₂ template particles, produced through molten‐flux synthesis, allowed precise control over their shape and dimensions, while the matrix was synthesized via a sol–gel synthesis. The integrated Na _x CoO ₂ particles of the textured composite exhibited increased thermal stability, showing no sign of decomposition at 1173 K in air, whereas the sole template particles decomposed at 1073 K during sintering. A 20 wt% template particle content in the textured composites resulted in a remarkably high and nearly temperature‐independent power factor of 8.8 µW cm ⁻¹ K ² , corresponding to an improvement of 13% compared to that of the pure matrix material.