Multi-layer graphene was produced through synthesized expanded graphite (EG) liquid exfoliation using organic solvent. Hexagonal graphite (HG) was used as a starting material. HG was mixed with an acidic mixture, dried, rand subjected to thermal treatment. After this process, EG was obtained. This obtained EG was sonicated for 1 h via an ultrasonic homogenizer by blending an organic solvent. Samples were subjected to SEM, TEM, FTIR, and UV-Vis/NIR spectroscopy investigations. After the investigations, it was shown that nano-size graphene sheets were obtained.

Multi-walled carbon nanotubes (MWCNTs) are a highly effective adsorbent of methylene blue (MB), and they can be used to remove MB from aqueous solutions. In this study, we used MWCNTs that were synthesized by chemical vapor deposition method. The physicochemical properties of MWCNTs were characterized by Brunauer-Emmett-Teller (BET) surface area, surface functional group analysis by fourier transform infrared (FTIR) analysis, zero point charge (pH_zpc), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The factors that affected the adsorption properties of MB onto MWCNTs were investigated, including initial pH, contact time, dosage, initial concentration, and temperature. The equilibrium adsorption data were analyzed using two common adsorption models, i.e. the Langmuir and Freundlich models. The results indicated that the Langmuir isotherm fits the experimental results well. The maximum adsorption capacity obtained from the equation of the Langmuir isotherm at 323 K was 95.30 mg/g, indicating that the MWCNTs adsorbed MB effectively. The kinetic study illustrated that the adsorption of MB onto MWCNTs fits the pseudo-second-order kinetic model. The thermodynamic parameters indicated that the adsorption of MB onto MWCNTs was a spontaneous, endothermic process.

One of the most promising solutions to slow down CO₂ emissions is the use of photocatalysis to produce hydrogen as a clean fuel. However, the efficiency of the photocatalysts is not at the desired level, and they usually need precious metal co-catalysts for reactions. In this study, to achieve efficient photocatalytic hydrogen production, a high-entropy oxide was synthesized by a mechano-thermal method. The synthesized high-entropy oxide had a bandgap of 2.45 eV, which coincided with both UV and visible light regions. The material could successfully produce hydrogen from water under light, but the main difference to conventional photocatalysts was that the photocatalysis proceeded without a co-catalyst addition. Hydrogen production increased with increasing time, and at the end of the 3 h period, 134.76 µmol/m² h of hydrogen was produced. These findings not only introduce a new method for producing high-entropy photocatalysts but also confirm the high potential of high-entropy photocatalysts for hydrogen production without the need for precious metal co-catalysts.