Synthesis of cerium and bismuth doped nickel aluminate for the photodegradation of methylene blue, methyl orange and rhodamine B dyes

In the current research, NiAl₂O₄, NiAl_1.98Bi_0.02O₄ and NiAl_1.98Ce_0.02O₄ are fabricated by the sol-gel method. Doping of larger ions (Ce³⁺ and Bi³⁺) into smaller aluminium ion lattice increased the lattice constant from 8.0091 Å to 8.9732 Å and 8.0272 Å respectively. XPS spectra of NiAl_1.98Ce_0.02O₄ confirmed the existence of Ce ion in Ce³⁺ and Ce⁴⁺. Spherical shaped particles with visible pores are noticed in the Transmission Electron Microscopy (TEM). The bandgap of the tailored materials has decreased to 2.25 eV and 2.98 eV and increased the catalytic efficiency due to the decrease in electron-hole pair recombination rate. The photocatalytic efficiency of the materials was tested against methylene blue (MB), methyl orange (MO) and rhodamine B (RhB) dyes. In the case of MB degradation, the efficiency of nickel aluminate (0.5 mg/mL) was 54% under UV light irradiation after 60 min, which was increased to 94% and 89% through cerium doped and bismuth doped nickel aluminate catalyst respectively. A drastic increase from 31% to 94% (NiAl_1.98Ce_0.02O₄) and 91% (NiAl_1.98Bi_0.02O₄) was noticed against MO degradation. Doping of cerium and bismuth in nickel aluminate enhanced the photocatalytic activity against the selected coloured organic pollutants.

Ultrasound assisted co-precipitation synthesis and catalytic performance of mesoporous nanocrystalline NiO-Al2O3 powders

Mesoporous nanocrystalline NiO-Al₂O₃ powders with high surface area were synthesized via ultrasound assisted co-precipitation method and the potential of the selected samples as catalyst was investigated in dry reforming reaction for preparation of synthesis gas. The prepared samples were characterized by N₂ adsorption (BET), X-ray diffraction (XRD), Temperature programmed reduction and oxidation (TPR, TPO) and scanning electron microscopy (SEM) techniques. The effects of pH, power of ultrasound irradiation, aging time and calcination temperature on the textural properties of the catalysts were studied. The sample prepared under specified conditions (pH10, 70W, without aging time and calcined at 600°C) exhibited the highest surface area (249.7m²g^-1). This catalyst was calcined at different temperature and employed in dry reforming of methane and the catalytic results were compared with those obtained over the catalysts prepared by impregnation and co-precipitation methods. The results showed that the catalyst prepared by ultrasound assisted co-precipitation method exhibited higher activity and stability with lower degree of carbon formation compared to catalysts prepared by co-precipitation and impregnation methods.