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Series of WO3/TiO2nanocomposites were obtained by hydrothermal method followed by calcination in the temperature range from 400°C to 900°C. The characteristics of photocatalysts by X-ray diffractometry (XRD), scanning electron microscope (SEM), and diffuse reflectance spectroscopy (DRS) showed that increasing the calcination temperature from 400 to 900°C resulted in change of photocatalytic activity under UV-Vis light. Moreover, the amount of WO3crystalline phase and amorphous phase in WO3/TiO2aggregates, as revealed by XRD analysis, was dependent on the calcination temperature. The WO3/TiO2samples with 8 mol% load of WO3in respect to TiO2calcinated at 500 and 800°C possess the highest photocatalytic activity in reaction of phenol degradation, which is about 1.2 and 1.5 times that with calcination at 400°C. The increase in calcination temperature above 400°C resulted in increase of WO3crystallinity and reduction of the amount of amorphous phase in the nanocomposite structure. Moreover, the annealing of nanocomposites above 700°C decreases the value of optical band gap energies of obtained WO3/TiO2nanomaterials.

Hydrogen-based technologies are among the most promising solutions to fulfill the zero-emission scenario and ensure the energy independence of many countries. Hydrogen is considered a green energy carrier, which can be utilized in the energy, transport, and chemical sectors. However, efficient and safe large-scale hydrogen storage is still challenging. The most frequently used hydrogen storage solutions in industry, i.e., compression and liquefaction, are highly energy-consuming. Underground hydrogen storage is considered the most economical and safe option for large-scale utilization at various time scales. Among underground geological formations, salt caverns are the most promising for hydrogen storage, due to their suitable physicochemical and mechanical properties that ensure safe and efficient storage even at high pressures. In this paper, recent advances in underground storage with a particular emphasis on salt cavern utilization in Europe are presented. The initial experience in hydrogen storage in underground reservoirs was discussed, and the potential for worldwide commercialization of this technology was analyzed. In Poland, salt deposits from the north-west and central regions (e.g., Rogóźno, Damasławek, Łeba) are considered possible formations for hydrogen storage. The Gubin area is also promising, where 25 salt caverns with a total capacity of 1600 million Nm3 can be constructed.

A sol-gel process followed by hydrothermal reaction was used to prepare coupled WO 3 -TiO 2 photocatalysts with varying amounts of WO 3 in respect to TiO 2 (3 mol% and 5 mol% respectively). Additionally, photocatalysts have been subjected to different calcination temperatures of 400ºC and 800ºC, which allowed us to compare how these affect photodegradation efficiency. Photocatalysts were characterized under a scanning electron microscope, x-ray diffraction, and by measuring BET surface area. Photocatalytic tests have been carried out following the degradation of toluene and cyclohexane in the gas phase under LED UV light (375 nm). Elevated calcination temperature turned to enhance photocatalytical efficiency of coupled WO 3 -TiO 2 while degrading the model pollutant cyclohexane. It was demonstrated that light emitting diodes (LEDs) can be used effectively as a source of illumination in photoreactors, sufficient to obtain 90% compound elimination from the air during 15 minutes of illumination while applying a wellmatched photocatalyst.

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