Effect of annealing temperature on the structural, morphological, photocatalytic and optical properties of the Cu-Ni co-doped TiO2 nanoparticles

The effect of annealing temperature on the photocatalyst's structural, morphological, photocatalytic and optical properties have been extensively studied. In this work, the Cu-Ni co-doped TiO2 powder was prepared by the sol-gel technique and annealed at temperatures 400°C, 500°C, 600°C, 700°C, and 800°C. The structural phase of the Cu-Ni/TiO2 changed from anatase to rutile after the annealing temperature increased from 400°C to 800°C. The anatase phase was found at 400°C and 500°C, the mixed phase at 600 and 700°C, and the rutile phase at 800°C. The specific surface area and band gap of Cu-Ni/TiO2 were decreased with the increment of annealing temperatures from 70.00 to 24.89 m2 /g and 3.36 eV to 3.04 eV, respectively. Meanwhile, as the annealing temperature rises, the average particle size increases from 38.52 to 173.59 nm. The anatase-rutile mixed phase of Cu-Ni/TiO2 annealed at 600°C exhibited the highest photocatalytic degradation of methylene blue (MB) with 62.81% MB removal. Experimental results indicated that the annealing temperature could alter the structural, morphological, and optical properties of the Cu-Ni/TiO2, affecting the photocatalytic activity performance.