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In order to extend the visible region activity of titania nanotube array (TNAs) films, the successive ionic layer adsorption and reaction (SILAR)-ultrasonication-assisted method has been used to prepare BiOI-modified TiO2 nanotube arrays (BiOI/TNAs). The band gap of BiOI/TNAs for all the variations reveals absorption in the visible absorption. The surface morphology of BiOI/TNAs is shown in the nanoplate, nanoflake and nanosheet forms with a vertical orientation perpendicular to TiO2. The crystalline structure of BiOI did not change the structure of the anatase TNAs, with the band gap energy of the BiOI/TNAs semiconductor in the visible region. The photocurrent density of the BiOI/TNAs extends to the visible-light range. BiOI/TNAs prepared with 1 mM Bi and 1 mM KI on TNAs 40 V 1 h, 50 V 30 min show the optimum photocurrent density. A tandem dye-sensitized solar cell (DSSC)-photoelectrochemical (PEC) was used for hydrogen production in salty water. BiOI/TNAs optimum was used as the photoanode of the PEC cell. The solar to hydrogen conversion efficiency (STH) of tandem DSSC-PEC reaches 1.34% in salty water.

Mg2+ doped ZnO has been successfully synthesized using a combination of sol-gel and sonochemical methods. Zinc acetate dihydrate was used as a precursor, magnesium chloride hexahydrate as a source of Mg dopant, methanol as a solvent, and chicken albumen was used as an additive to replace monoethanolamine. The sol was heated at 110 °C for 1 hour. The gel formed was calcined at 600 °C for 3 hours. FTIR analysis shows that the absorbance band around 400-450 cm-1 indicates Mg-O stretching, the absorbance band around 500-550 cm-1 indicates Zn-O stretching, the absorbance band around 400-550 cm-1 shows Zn-O-Mg bonds. Mg. Measurements with UV-DRS, obtained the smallest ZnO band gap value doped Mg2+ around 2.7 eV with the addition of 10 mL albumen. The resulting crystal structure was wurtzite with crystal size with the addition of 10, 20, 30, 40 and 50 mL albumen were 25.22-55.91 nm, 32.99-75.87 nm, 45.92-83.91 nm, 45.92-75.89 nm and 46.15-71.47 nm respectively. SEM photo of Mg2+ doped ZnO with the addition of 10 mL of albumen has a hexagonal surface morphology.

Cu2+ doped ZnO by green synthesis was successfully prepared by using a combination of the Sol-Gel-Sonochemical method. Duck egg albumen was used as an additive, a substitute for chemical additives, such as monoethanolamine (MEA) and diethanolamine (DEA). Zn(CH3COO)2·2H2O was used as a precursor, Cu(CH3COO)2·H2O was used as a dopant source with concentrations of 5 wt.%, and isopropanol was used as the solvent. The addition of albumen variations was 10, 20, 30, 40, and 50 mL. The prepared catalyst was applied for the degradation of the methyl orange dyes by using photosonolysis with variations of the degradation time of methyl orange for 30, 60, 90, 120, 150, 180, and 240 min. FTIR spectra showed stretching at 400–550 cm–1 indicating the presence of Zn–O and Zn–O–Cu metal oxides. The optimum bandgap energy value was 2.82 eV with the addition of 30 mL of albumen. XRD analysis showed the optimum particle size of 16.62–53.21 nm after adding 30 mL of additives. The SEM image showed a spherical shape with an average diameter of 2.7 μm. The optimum percentage of degradation obtained was 94.88%, with the irradiation time under UV light for 210 min.

Nickel oxide (NiO) nanocrystals were synthesized by simple sol-gel method at low temperature by using methanol as the solvent and NaOH 5M as the precipitation agent. Nickel nitrate hexahydrate, nickel acetate tetrahydrate and nickel sulfate hexahydrate were used as the precursors. The crystals were formed by drying at 100-110 C for 1 hour, after which they were heated at 450 C for 1 hour. The resulting products were black powders. The as-prepared NiO nanocrystals were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD patterns of the NiO nanocrystals showed that they are mostly cubic. The sizes of the NiO particles produced with nickel nitrate hexahydrate, nickel acetate tetrahydrate and nickel sulfate hexahydrate were 72.16, 38.63 and 32.84 nm, respectively. SEM images showed that the nanopowders produced by the precursors are spherical, rod-shaped and hexagonal shape with hollow, respectively.

Synthesis of nickel oxide (NiO) with various solvents by simple sol-gel process has been done. NiO nanopowders were obtained by using nickel nitrate hexahydrate and sodium hydroxide 5 M were used as precursor and agent precipitator, respectively. The addition of various solvents that used in this research were aquadest, methanol and isopropanol. The powders were formed by drying in the temperature of 100-110 °C for 1 h and after heating at ±450 °C for 1 h. The products were obtained black powders. The products were characterized by Energy Dispersive X-Ray Fluorescence (ED-XRF), X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The ED-XRF pattern show that composition of NiO produced was 96.9%. The XRD patterns showed NiO forms were in monoclinic structure with aquadest solvent and cubic structure with methanol and isopropanol used. Crystal sizes of NiO particles produced with aquadest, methanol, isopropanol were obtained in the range 37.05; 72.16; 66.04 nm respectively. SEM micrograph clearly showed that powder had a spherical shape with uniform distribution size is 0.1-1.0 µm approximately.