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Nowadays, ammonia is viewed as the prospective green hydrogen fuel carrier. Yet, there still is a demand for active, energy-efficient NH3 synthesis catalysts to make ammonia use economically viable. This paper studies and discusses lanthanide oxide-supported cobalt catalysts for low-pressure ammonia synthesis, which are intended to be a model for prototyping systems alternative to ruthenium-based catalysts. In the Co/Ln2O3 system, lanthanide oxide is a support and an electronic promoter. The electron density on the active phase’s surface is increased through Strong Metal-Support Interactions and the formation of oxygen-deficient, Ln2O3−x species capable of electron donation. In the systems, electronic promotion strength depends on the Ln3+ cation and the support conductivity, catalyst Turnover Frequency and basicity increase exponentially with the increase of the Ln3+ ionic radius. These dependencies enable the design of novel cobalt catalysts of specific properties and outline the prospects for their further development.

Our study reports the ultrasound-assisted synthesis of SnS and SnS2 in the form of nanoparticles using aqueous solutions of respective tin chloride and thioacetamide varying sonication time. The presence of both compounds is confirmed by powder X-ray diffraction, energy-dispersive X-ray spectroscopy, as well as Raman and FT-IR spectroscopic techniques. The existence of nanoparticles is proven by powder X-ray diffraction investigation and by high resolution transmission electron microscopy observations. The size of nanocrystallites are in the range of 3–8 nm and 30 50 nm for SnS, and 1.5–10 nm for SnS2. X-ray photoelectron spectroscopy measurements, used to investigate the chemical state of tin and sulphur atoms on the surface of nanoparticles, reveal that they are typically covered with tin on the same oxidation degree as respective bulk compound. Values of optical bandgaps of synthesized nanoparticles, according to the Tauc method, were 2.31, 1.47 and 1.05 eV for SnS (60, 90 and 120 min long synthesis, respectively), and 2.81, 2.78 and 2.70 eV for SnS2 (60, 90 and 120 min long synthesis, respectively). Obtained nanoparticles were utilized as photo- and sonocatalysts in the process of degradation of model azo-dye molecules by UV-C light or ultrasound. Quantum dots of SnS2 obtained under sonication lasting 120 min were the best photocatalyst (66.9 % color removal), while quantum dots of SnS obtained under similar sonication time were the best sonocatalyst (85.2 % color removal).

Abstract Topological electronic materials hold great promise for revolutionizing spintronics, owing to their topological protected, spin‐polarized conduction edge or surface state. One of the key bottlenecks for the practical use of common binary and ternary topological insulator materials is the large defect concentration that leads to a high background carrier concentration. Elemental tin in its α‐phase is a room temperature topological semimetal, which is intrinsically less prone to defect‐related shortcomings. Recently, the growth of ultrathin α‐Sn films on ferromagnetic Co surfaces has been achieved; however, thicker films are needed to reach the 3D topological Dirac semimetallic state. Here, the growth of α‐Sn films on Co at cryogenic temperatures was explored. Very low‐temperature growth holds the promise of suppressing undesired phases, alloying across the interfaces, as well as the formation of Sn pillars or hillocks. Nevertheless, the critical Sn layer thickness of ≈3 atomic layers, above which the film partially transforms into the undesired b‐phase, remains the same as for room‐temperature growth. From ferromagnetic resonance studies, and supported by electron microscopy, it can be concluded that for cryogenic Sn layer growth, the interface between Sn and Co remains sharp and the magnetic properties of the Co layer stay intact.