Construction of novel AgIO4/ZnO/graphene direct Z-scheme heterojunctions for exceptional photocatalytic hydrogen gas production

Through sonochemical route, hybrid AgIO4/ZnO/graphene heterojunctions were successfully fabricated for photoproduction of hydrogen gas. The physicochemical features of these hybrid photocatalysts were assessed by XRD, N2-adsorption–desorption isotherm, DRS, PL, XPS and HRTEM. Particularly, ZnO and AgIO4 nanoparticles are concentrated on the wrinkled points of crumbled graphene sheets due to the functionality of these active sites. Various observations reveal the heterojunction construction as pronounced shifting in ZnO main diffraction peaks to lower two theta values, reduction in PL signal intensity and increase in the sample surface area. Using methanol as scavenger, the evolution rate reaches 16.4 mmolh−1 g−1 that is fivefold higher compared with bare ZnO nanoparticles. The production in hydroxyl radical (EVB =  + 2.88 eV) that is recorded from PL measurements of terephthalic acid indicates the charge migration was predominant proceeding through direct Z-scheme mechanism rather than type (II) heterojunction traditional route. The direct Z-scheme mechanism reveals that the fast hydrogen evolution rate was attributed to the charge migration and noticeable oxidative and reductive power of the charge carriers. The novel nanocomposite is considered a promising material for photoproduction of hydrogen gas on large scale.