Experimental and first-principle insight into Structural, optical and electrical properties and photocatalytic water purification application of Zn1-xMgxO

[Display omitted] •Mg-doped ZnO synthesized by ball milling cum solid state reaction technique.•Impact of Mg content on structural, optical and electrical/dielectric properties.•DFT + U calculations used to determine the structure, DOS and band structure.•Degradation of methylene blue and Congo red using samples as Photocatalysts. Environmental concern essentially demands solemn consideration of industrial waste-water containing organic dyes. To develop efficient photocatalysts for degradation of organic dyes in waste water, metal-oxide nanostructures are the promising candidate owing to their tunable physical properties. The present work emphasizes on the experimental and first-principle (DFT + U) studies to understand the impact of magnesium doping on the structural, optical and electrical properties, and photocatalytic degradation tendency of zinc oxide (ZnO) nano-ceramics. The ZnO lattice contraction endorsed by Mg-doping, has been examined mutually from the first principle calculations and Rietveld refinement investigations. The decrease in crystallite-size (93 to 88 nm) and enrichment in structural imperfections of Zn1-xMgxO nanostructures were analyzed with Williamson-Hall peak profile methods. The band gap broadening of ZnO with Mg doping was demonstrated by UV–visible spectroscopy (3.32 to 3.43 eV) which was further confirmed from DFT + U (3.39 to 3.55 eV) calculations. The increase in dielectric constant and reduction in ac conductivity has been observed due to Mg addition. The photocatalytic performance of Zn1-xMgxO nanostructures was evaluated under sunlight for Methylene-blue (MB) and Congo-red (CR) dyes. The performance has been optimally improved with 6 mol% Mg content leading to degradation of 86.2 % and 58.3 % of MB and CR dyes respectively in 160 min.