Aleksandra Pacuła

N- and Fe-containing carbon-based materials were prepared at 600 and 700 °C via catalytic chemical vapor deposition (CCVD) with acetonitrile (as carbon and nitrogen source) with the application of metal/metal oxides generated in situ from Mg–Fe–Al hydrotalcite-like materials (HTs). The impact of synthesis temperature and transition metal (Fe) concentration in a blend of metal oxides derived from HTs on carbon deposit content and its structural ordering, nitrogen doping, location of N-containing groups in graphitic array, morphology and porosity was investigated using XRD, EA, XRF, XPS, SEM, HR-TEM, Raman and Mössbauer spectroscopy, and N₂ sorption. Higher synthesis temperature and increased concentration of Fe-containing species occurring in a mixture of metal oxides derived from Mg–Fe–Al HTs enhanced the quantity of carbonaceous product, the mesopore volume and the thickness of graphitic domains occurring in the carbon materials and lowered nitrogen doping extent in carbon framework. Enhanced accessibility to active sites via pore network, as well as, improved electrical conductivity associated with increased graphitic domain thickness and reduced amorphous carbon content were found to be critical factors in their performance for oxygen reduction reaction (ORR) in alkaline electrolyte. No direct correlation between the population of N-containing species and ORR activity is observed but the presence of quaternary N appears to enhance selectivity for the 4-electron pathway. In addition, the influence of the carbon materials dispersed in polymer matrix in polycaprolactone (PCL)-based composite films on bulk (conductivity, dielectric constant) and surface (morphology, topography, roughness and water contact angle) properties was also described. Graphical abstract

Layered double hydroxides (LDHs) of various compositions, i.e. Mg–Al, Mg–Mn–Al, are applied as the precursors of metal oxides for the preparation of N-doped carbon materials via chemical vapour deposition (CVD) with acetonitrile (as carbon and nitrogen source) at 600 and 700 °C. The use of Mn-containing LDHs for the preparation of the carbon materials is a novelty. The impact of transition metal species, i.e. Mn_xO_y, in a blend of metal oxides derived from LDHs on the amount of carbon deposit and its composition, morphology, textural and capacitive properties is investigated. Mn-containing species occurring in a mixture of metal oxides enhance the quantity of carbonaceous product compared to those derived from Mg–Al LDHs. Thermally heated Mg–Mn–Al LDHs contain structural defects due to manganese oxides, which promote the formation of carbon deposit, especially higher production of amorphous carbons. The addition of Mn into Mg–Al LDHs matrix leads to carbon particles with increased N-doping and enhanced volume of mesopores. Furthermore, graphitic domains occurring in the carbon materials obtained with Mg–Mn–Al LDHs are thicker than those in the corresponding samples obtained with Mg–Al LDHs as Mn-containing species influence the concentration and location of N-containing groups in graphitic array. The specific capacitance of the carbon materials produced by CVD with the compounds derived from Mg–Al LDHs or Mg–Mn–Al LDHs is comparable (20–25 μF cm⁻²). The formation of electrical double layer at electrode/electrolyte interface is easier for the carbon materials prepared at 700 °C than for the carbon materials prepared at 600 °C. The maximum charge is stored either in the shallow parts of carbon particles for the former, as they contain bottleneck mesopores, or in the deep parts of carbon particles for the latter, as they contain slit-shaped mesopores. Graphical abstract

Immobilization of photocatalysts in porous materials is an approach to significantly minimize the hazards of manipulation and recovery of nanoparticles. Inorganic materials, such as zeolites, are proposed as promising materials for photocatalyst immobilization mainly due to their photochemical stability. In this work, a green synthesis method is proposed to combine TiO₂-based photocatalysts with commercial ZY zeolite. Moreover, a preliminary analysis of their performance as photocatalysts for the abatement of organic pollutants in waters was performed. Our results show that the physical mixture of TiO₂ and zeolite maintains photocatalytic activity. Meanwhile, composites fabricated by doping TiO₂–zeolite Y materials with silver and palladium nanoparticles do not contribute to improving the photocatalytic activity beyond that of TiO₂.