In-situ formation of a ZnO@graphene oxide nanocomposite from alginate xerogels with enhanced photocatalytic performance

Abstract

A smart eco-design approach for the synthesis of a zinc oxide@graphene oxide (ZnO@GO) nanocomposite was developed. The approach involved heat treatment by calcination of zinc- alginate xerogels at 600 °C for 8 h under argon atmosphere, followed by sonication in order to exfoliate the graphite oxide formed by calcination into graphene oxide. Key exfoliation parameters (duration, power, and ethanol/water ratio) were optimized according to a three- factor Doehlert matrix design. Systematic variations of exfoliation factors were undertaken to assess their impact on the photocatalytic activity of ZnO@GO nanocomposites. Photocatalytic performances of the innovative ZnO@GO nanocomposite catalyst were tested on the photodegradation of Orange G model dye under UV light irradiation. and complete degradation of Orange G was achieved after 135 min. Photocatalysis mediated by the as- prepared nanocomposite exhibited a rate constant of 0.0429 min −1 , which was higher than photocatalysis mediated by pristine ZnO nanoparticles at a rate constant of 0.0255 min −1 . Furthermore, ZnO@GO showed improved performance and reliable reproducibility in dye photodegradation, with a decrease in performance of only 11.6% following 7 reaction cycles. • An eco-design strategy enabled synthesis of ZnO@GO from zinc–alginate xerogels. • Exfoliation parameters optimized using a three-factor Doehlert design. • ZnO@GO achieved complete Orange G photodegradation under UV in 135 min. • ZnO@GO showed higher photocatalytic rate constant than pristine ZnO. • ZnO@GO showed good stability with only 11.6% loss after seven cycles.