Gd(OH)₃ and Co-Doped Gd(OH)₃ for Photocatalytic Degradation of 4-Nitrophenol and Brilliant Green

The microwave-assisted synthesis method was used to synthesize gadolinium hydroxide nanorods (GH NRs) and 4-12% cobalt-doped gadolinium hydroxide nanorods (4CGH, 8CGH, and 12CGH NRs). X-ray diffraction confirmed that the GH NRs and CGH NRs are in the hexagonal phase with average crystallite sizes between 17 and 36 nm. Raman and FT-IR spectra confirmed the presence of vibrational modes of GH and CGH. The influence of Co doping was observed in the reduction of the band gap energy from 5.00 to 4.29 eV. TEM images showed nanorods of GH and CGH and that the particle size was increased upon doping with Co²⁺. Photocatalytic degradations of 4-nitrophenol (4-NP) and brilliant green (BG) were carried out under UV light irradiation in which 8CGH NRs had the highest photocatalytic degradation of BG (90%) with a kinetic rate of 0.4636 h^-1, while 12CGH NRs showed the highest photocatalytic degradation of 4-NP (78%) with a kinetic rate of 0.2426 h^-1. Both photocatalytic degradation activities using the synthesized materials followed a pseudo-first-order kinetic reaction. Therefore, GH and CGH NRs demonstrated efficient application under UV light irradiation.