Enhanced solar light photocatalytic properties of ZnO nanocrystals by Mg-doping via polyacrylamide polymer method

[Display omitted] •Synthesis of Mg-doping ZnO by facile polyacrylamide gel method.•Tailoring ZnO band gap and surface properties by alloying with 5 at.% Mg2+.•MZO decomposes 95% MB solution within 45min under solar irradiation.•MZO maintains more than 95% photodegradation after nine cycles.•Lowest oxygen vacancies of MZO favor for preventing electron-hole recombination. The photocatalytic performance of Mg-doped ZnO (MZO) nanoparticles, synthesized through the polyacrylamide polymer method, was investigated by the photodegradation of the methylene blue (MB) solution. The nanoparticles were characterized by X-ray diffractometry, X-ray photoelectron spectroscopy, and UV–vis absorption spectrum. The results demonstrate that the catalysts present different photodegradation performances with varying calcination temperatures of the as-synthesized Mg-doped ZnO precursor. It is found that the highest photodegradation of the MB solution was achieved by the catalyst with a 47nm particle size, which had the lowest oxygen vacancies. The influence of operational parameters of pH and initial dye concentration was evaluated. Catalyst activity remained at 95% of its initial value even after the photodegradation process was repeated for nine times. Moreover, three intermediate products, possessing the OH, O2− and h+ groups were detected in the photodegradation processes. Hence, we attribute the enhanced photocatalytic properties of the ZnO nanoparticles to the lower amount of oxygen vacancies, which are a consequence of Mg-doping preventing electron-hole recombination.