Influence of gadolinium substitution on the crystal structure of NiO and its maximized photocatalytic degradation activity on tetracycline and direct yellow pollutants

Abstract

Gadolinium-substituted NiO crystal structures with excellent stability were utilized for the first time to degrade antibiotic and organic dye pollutants. A simple hydrothermal technique was used to synthesize different concentrations of Gd3+ substituted NiO, and the catalysts were thoroughly characterized using sophisticated techniques to explore the influence of Gd3+ on the crystal structure and optical characteristics of NiO. The 1.5% Gd3+ substituted NiO showed outstanding photocatalytic activity on tetracycline and direct yellow degradation, with percentages of 90.72 and 95.5%, respectively. The improvement of photocatalytic degradation efficiency is primarily due to the suppression of photoinduced electron and hole recombination via the creation of Gd3+ as the inner energy band state below the conduction band. The recycling experiments revealed that the catalyst is more stable, with no indication of loss after ten cycles. Scavenging investigations also demonstrated that superoxide and holes were responsible for the efficient degradation of pollutants.