Ingenieurwissenschaften und zugeordnete Tätigkeiten
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- 2022 (2)
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- Catalysis (1)
- Core-shell (1)
- Halide Perovskites (1)
- MAPbI3 perovskites (1)
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ABX3 metal halide perovskites revolutionized the research and development of new optoelectronics, including solar cells and light-emitting diodes. Processing polycrystalline thin films from precursor solutions is one of the core advantages of these materials since it enables versatile and cost-effective manufacturing. The perovskite film morphology, that is, continuous substrate coverage and low surface roughness, is of paramount importance for highly efficient solar cells and optoelectronic devices in general. Controlling the chemistry of precursor solutions is one of the most effective strategies to manage the perovskite film morphology. Herein, we show the fundamental influence of the A-site cation composition on the perovskite precursor arrangement and the consequent film formation. Extended X-ray absorption fine structure spectroscopy and small-angle X-ray scattering give unprecedented insights into the complex structural chemistry of the perovskite precursors and, in particular, their repulsive interactions as a crucial parameter for colloidal stability. Combining these techniques with in situ grazing incidence wide-angle X-ray scattering during thin-film formation allows us to identify the mechanism for using alkali metals as a decisive criterion to control the colloidal stability of the perovskite precursor and thus the thin-film morphology. We illustrate the fundamental principle behind the systematic use of alkali metals regardless of whether they are incorporated in the lattice or not. Hence, this work provides tools to selectively control the morphology and crystal growth in present and future systems
A facile and efficient methodology is described for the solvothermal synthesis of size-tunable, stable, and uniform NiCu core–shell nanoparticles (NPs) for application in catalysis. The diameter of the NPs is tuned in a range from 6 nm to 30 nm and to adjust the Ni:Cu ratio from 30:1 to 1:1. Furthermore, the influence of different reaction parameters on the final NPs is studied. The NPs are structurally characterized by a method combination of transmission electron microscopy, anomalous small-angle X-ray scattering, X-ray absorption fine structure, and X-ray photoelectron spectroscopy. Using these analytical methods, it is possible to elucidate a core–shell–shell structure of all particles and their chemical composition. In all cases, a depletion from the core to the shell is observed, with the core consisting of NiCu alloy, surrounded by an inner Ni-rich shell and an outer NiO shell. The SiO2-supported NiCu core–shell NPs show pronounced selectivity of >99% for CO in the catalytic reduction of CO2 to CO using hydrogen as reactant (reverse water–gas shift reaction) independent of size and Ni:Cu ratio.