Effective substitution of La³⁺ on the NiO crystal structure for the augmentation of photocatalytic tetracycline and Congo red degradation

In this study, different concentrations of La³⁺-substituted NiO nanocatalysts were synthesized through a simple precipitation technique and characterized well with sophisticated instruments. The photocatalytic activity of the La-NiO-1.5% catalyst was substantially higher than that of pristine, 0.5%, 1%, and 2% La³⁺-substituted NiO samples for the degradation of tetracycline antibiotic pollutant (84.3%) and Congo red aqueous dye (90.2%). The increased efficiency could be attributed to a decrease in photo-induced electron–hole recombination rate by the formation of the La³⁺ inner energy state. The recycling tests show that the La-NiO-1.5% samples have excellent stability for both CR and TC aqueous pollutant degradation, and the scavenging analysis shows that the \(\cdot {\text{O}}^{2-}\) $·{\text{O}}^{2-}$ and \(\cdot \text{OH}\) $·\text{OH}$ radicals are the primary active radicals for degradation. The possible photocatalytic reaction mechanism was established by the characterization findings.