In this work, a synthesis technique for highly homogeneous PVDF-CaFe₂O₄ polymer films direct from solution was developed. The structural characterizations were conducted using XRD, FTIR, and ESEM experimental techniques. The XRD characteristic peaks of CaFe₂O₄ nanoparticles revealed a polycrystalline structure. The average crystallite size for CaFe₂O₄ was calculated to be 17.0 nm. ESEM micrographs of PVDF nanocomposites containing 0.0, 0.25, 0.75, and 1.0 wt% of CaFe₂O₄ showed smooth surface topography. The direct E_dir and indirect E_ind band gap energies for the PVDF-CaFe₂O₄ nanocomposites were decreased with the additions of 0.0–1.0 wt% CaFe₂O₄. In addition, the refractive index (n₀) increased from 3.38 to 10.36, and energy gaps (E_g) decreased from 5.50 to 4.95 eV. The nonlinear refractive index (n₂) for the PVDF-CaFe₂O₄ nanocomposites was improved with the addition of CaFe₂O₄ nanoparticles, exceeding those reported in the literature for PVC, PVA, and PMMA nanocomposites. Therefore, the PVDF-CaFe₂O₄ nanocomposites are expected to take the lead in optoelectronic applications because of their unusual optical properties.

The nanocomposites of S@g-C₃N₄ and NiS-g-C₃N₄ were synthesized for catalytic hydrogen production from the methanolysis of sodium borohydride (NaBH₄). Several experimental methods were applied to characterize these nanocomposites such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and environmental scanning electron microscopy (ESEM). The calculation of NiS crystallites revealed an average size of 8.0 nm. The ESEM and TEM images of S@g-C₃N₄ showed a 2D sheet structure and NiS-g-C₃N₄ nanocomposites showed the sheet materials that were broken up during the growth process, revealing more edge sites. The surface areas were 40, 50, 62, and 90 m²/g for S@g-C₃N₄, 0.5 wt.% NiS, 1.0 wt.% NiS, and 1.5 wt.% NiS, respectively. The pore volume of S@g-C₃N₄ was 0.18 cm³, which was reduced to 0.11 cm³ in 1.5 wt.% NiS owing to the incorporation of NiS particles into the nanosheet. We found that the in situ polycondensation preparation of S@g-C₃N₄ and NiS-g-C₃N₄ nanocomposites increased the porosity of the composites. The average values of the optical energy gap for S@g-C₃N₄ were 2.60 eV and decreased to 2.50, 2.40, and 2.30 eV as the NiS concentration increased from 0.5 to 1.5 wt.%. All NiS-g-C₃N₄ nanocomposite catalysts had an emission band that was visible in the 410–540 nm range and the intensity of this peak decreased as the NiS concentration increased from 0.5 to 1.5 wt.%. The hydrogen generation rates increased with increasing content of NiS nanosheet. Moreover, the sample 1.5 wt.% NiS showed the highest production rate of 8654 mL/g·min due to the homogeneous surface organization.

In this work, the S@g-C₃N₄ and CuS@g-C₃N₄ catalysts were prepared via the polycondensation process. The structural properties of these samples were completed on XRD, FTIR and ESEM techniques. The XRD pattern of S@g-C₃N₄ presents a sharp peak at 27.2° and a weak peak at 13.01° and the reflections of CuS belong to the hexagonal phase. The interplanar distance decreased from 0.328 to 0.319 nm that facilitate charge carrier separation and promoting H₂ generation. FTIR data revealed the structural change according to absorption bands of g-C₃N₄. ESEM images of S@g-C₃N₄ exhibited the described layered sheet structure for g-C₃N₄ materials and CuS@g-C₃N₄ demonstrated that the sheet materials were fragmented throughout the growth process. The data of BET revealed a higher surface area (55 m²/g) for the CuS-g-C₃N₄ nanosheet. The UV–vis absorption spectrum of S@g-C₃N₄ showed a strong peak at 322 nm, which weakened after the growth of CuS at g-C₃N₄. The PL emission data showed a peak at 441 nm, which correlated with electron–hole pair recombination. The data of hydrogen evolution showed improved performance for the CuS@g-C₃N₄ catalyst (5227 mL/g·min). Moreover, the activation energy was determined for S@g-C₃N₄ and CuS@g-C₃N₄, which showed a lowering from 47.33 ± 0.02 to 41.15 ± 0.02 KJ/mol.

The synthesis of CaCO₃/Cu₂O/GO nanocomposites was developed by sol-gel auto-combustion method. The analysis of structure was completed on X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and environmental scanning electron microscopy (ESEM). The XRD spectra of the nanocomposites matched the crystal structure of CaCO₃/Cu₂O. The average crystal size was 20 nm for Cu₂O and 25 nm for CaCO₃ nanoparticles. FTIR data showed the absorption bands of Cu₂O and GO. Raman spectroscopy data confirmed the formation of GO sheets. ESEM micrographs displayed spherical nanoparticles dispersed in GO sheets. X-ray photoelectron spectroscopy showed the peaks of Cu 2p, O 1s, C 1s, Cu 3s, and Ca 2p. The spectra of optical absorption revealed an absorption band of around 450 nm. The calcium content increase led to a decrease in the optical energy gap from 2.14 to 1.5 eV. The production of hydrogen from NaBH₄ across the methanolysis reaction was accelerated by the CaCO₃/Cu₂O/GO nanocomposites. Therefore, these nanocomposites are superior in catalytic hydrogen production systems.

Hydrogen production as a source of clean energy is high in demand nowadays to avoid environmental issues originating from the use of conventional energy sources i.e., fossil fuels. In this work and for the first time, MoO₃/S@g-C₃N₄ nanocomposite is functionalized for hydrogen production. Sulfur@graphitic carbon nitride (S@g-C₃N₄)-based catalysis is prepared via thermal condensation of thiourea. The MoO₃, S@g-C₃N₄, and MoO₃/S@g-C₃N₄ nanocomposites were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Field Emission Scanning Electron Microscope (FESEM), STEM, and spectrophotometer. The lattice constant (a = 3.96, b = 13.92 Å) and the volume (203.4 ų) of MoO₃/10%S@g-C₃N₄ were found to be the highest compared with MoO₃, MoO₃/20-%S@g-C₃N₄, and MoO₃/30%S@g-C₃N₄, and that led to highest band gap energy of 4.14 eV. The nanocomposite sample MoO₃/10%S@g-C₃N₄ showed a higher surface area (22 m²/g) and large pore volume (0.11 cm³/g). The average nanocrystal size and microstrain for MoO₃/10%S@g-C₃N₄ were found to be 23 nm and −0.042, respectively. The highest hydrogen production from NaBH₄ hydrolysis ~22,340 mL/g·min was obtained from MoO₃/10%S@g-C₃N₄ nanocomposites, while 18,421 mL/g·min was obtained from pure MoO₃. Hydrogen production was increased when increasing the masses of MoO₃/10%S@g-C₃N₄.

This study aims to prepare new nanocomposites consisting of Cr₂O₃/CaCO₃ as a catalyst for improved hydrogen production from NaBH₄ methanolysis. The new nanocomposite possesses nanoparticles with the compositional formula Cr_2−xCa_xO₃ (x = 0, 0.3, and 0.6). These samples were prepared using the sol-gel method, which comprises gelatin fuel. The structure of the new composites was studied using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, environmental scanning electron microscopy (ESEM), and X-ray spectroscopy (XPS). The XRD data showed the rhombohedral crystallinity of the studied samples, and the average crystal size was 25 nm. The FTIR measurements represented the absorption bands of Cr₂O₃ and CaO. The ESEM micrographs of the Cr₂O₃ showed the spherical shape of the Cr₂O₃ nanoparticles. The XPS measurements proved the desired oxidation states of the Cr_2−xCa_xO₃ nanoparticles. The optical band gap of Cr₂O₃ is 3.0 eV, and calcium doping causes a reduction to 2.5 and 1.3 eV at 15.0 and 30.0% doping ratios. The methanolysis of NaBH₄ involved accelerated H₂ production when using Cr_2−xCa_xO₃ as a catalyst. Furthermore, the Cr_1.7Ca_0.3O₃ catalyst had the highest hydrogen generation rate, with a value of 12,750 mL/g/min.