One of the most important goals of modern materials science is the development of efficient catalytic and photocatalytic materials for applications in environmental protection and renewable energy sources. Intensive research and creation of new photocatalytic materials are being carried out to enable the efficient decomposition of organic pollutants using sunlight. Also, great efforts are being made in the development of photocatalytic and electrocatalytic materials that would be used for the photoelectrochemical production of hydrogen by splitting water molecules using sunlight, which is at the same time a renewable and clean source of energy. It is desirable that the catalysts used for the above reactions are made of chemical elements that are not very expensive with abundant supplies in nature (unlike platinum metals, which are excellent catalysts, but are very expensive with limited supplies), that are stable under the conditions of the catalytic reaction and that are not harmful to the environment. Due to its stability, non-toxicity, low cost, abundant natural resources, and energy band gap of about 2.1 eV (which allows the absorption of a large part of sunlight), the iron oxide hematite (α-Fe2O3) is a suitable material for application in the photocatalytic degradation of organic pollutants and photoelectrochemical water splitting using sunlight. However, the short lifetime and poor mobility of photogenerated charge carriers (electrons and holes) severely limit its photocatalytic activity. The use of elongated (1D) hematite nanoparticles increases the mobility of photogenerated charge carriers, reduces their recombination rate, and reduces their average distance from the surface where the reaction occurs, which increases photocatalytic activity. Doping hematite with divalent and tetravalent metal cations can also increase the mobility of charge carriers and thus improve its photocatalytic properties. Since carbon nanomaterials are excellent charge conductors and electron acceptors, their composites with metal oxide nanoparticles have improved transport and reduced recombination of charge carriers, which affects the improvement of photocatalytic properties. Nanostructured mixed hydroxides and oxides of nickel and iron (Ni(OH)2 and NiO doped with Fe, NiFe2O4) showed excellent properties as electrode materials for the oxygen evolution reaction (OER), which is essential for the efficient production of hydrogen by splitting water molecules. However, due to the low conductivity of these materials, when making electrodes, it is necessary to mix them with conductive materials. Carbon nanomaterials are excellent charge conductors, and their composites with nanoparticles of metal hydroxides and oxides should have improved electrocatalytic properties. Within this project, new advanced composite materials consisting of metal oxide nanoparticles (1D α-Fe2O3 nanoparticles doped with selected metal cations, nanoparticles of mixed Ni-Fe hydroxides and oxides) and various carbon nanomaterials (graphene, graphene oxide, carbon nanotubes, multi-walled nanotubes and nanoribbons, etc.) will be synthesized. Composites of metal oxide nanoparticles and carbon nanomaterials will be synthesized in two ways: a) by hydrothermal treatment of a suspension of carbon nanomaterials in an aqueous solution of a metal salt and b) by hydrothermal treatment of a suspension of metal oxide nanoparticles and carbon nanomaterials. The obtained composites will be characterized using several instrumental techniques (XRPD - crystal structure and crystallite size, FE-SEM - particle size and shape, Mössbauer spectroscopy - phase composition, local structure and oxidation state of Fe atoms, SQUID magnetometer - magnetic properties, UV-Vis-NIR spectroscopy - absorption of UV, visible and near IR, FT-IR spectroscopy - absorption of mid and far IR radiation, TGA - thermal properties). Photocatalytic properties will be determined by testing the degradation of model organic pollutants (reactive dyes and various pesticides). Various parameters will be optimized in order to obtain a cheap, efficient and environmentally friendly procedure. Electrocatalytic properties will be determined using the most modern electrochemical methods (cyclic voltammetry, electrochemical impedance spectroscopy, potentiostatic and galvanostatic polarization). The obtained results will be compared with the results from the literature. The aim of this project is to prepare an environmentally friendly and stable composite material of metal oxide nanoparticles and carbon nanomaterials with improved photocatalytic or electrocatalytic properties. The influence of the type and content of the metal cation (Ni2+, Cu2+, Co2+, Mn2+, Zn2+, etc.) incorporated into 1D hematite nanoparticles and the type of carbon nanomaterial on the photocatalytic properties of their composites will be investigated. The influence of the content of Ni and Fe, the crystal structure and particle size of mixed Ni-Fe hydroxides and oxides, and the type of carbon nanomaterial on the electrocatalytic properties of their composites will also be investigated. It is expected that the composite materials will show better photocatalytic and electrocatalytic properties than the metal oxide nanoparticles themselves due to better mobility of charge carriers and reduced recombination. In addition, this project aims to maintain, intensify and expand the existing collaboration between research groups from the Ruđer Bošković Institute (RBI) and the Institute for Nuclear Sciences "Vinča". Research groups from the RBI and the Vinča Institute have been collaborating for several years in research on the properties of metal oxide nanoparticles, which has resulted in the publication of several joint publications (Ceram Int. 39 (2013) 6681, J. Phys. Chem. C 116 (2012) 4356, J. Alloys Compd. 634 (2015) 130, J. Alloys Compd. 750 (2018) 687). The proposed project fits into the latest research directions in materials science, and continued cooperation between the two research groups can be expected within regional or EU H2020 projects.