Investigation of Diazinon degradation via advanced photocatalysis of CoWO4/g-C3N4 Z scheme heterojunction with addition of H2O2

CoWO4, a relatively positive valence band semiconductor, has been coupled with g-C3N4, a relatively negative conduction band semiconductor, to establish a Z-scheme heterojunction. The photocatalytic tests indicated that the Diazinon removal efficiency of the heterojunction was 71.6 %, which was remarkably higher than those of the pristine CoWO4 (63.0 %) and g-C3N4 (61.1 %). This was because of Z-scheme mechanism, which photo-excited e- at the CoWO4 Cband migrated to the g-C3N4 Vband to preserve e- at the g-C3N4 Cband and h+ in the CoWO4 Vband. Then, remained e- and h+ with strong re-dox ability respectively reacted with O2 and H2O to generate O2•- and •OH radicals to degrade Diazinon. The study also investigated that H2O2 effectively acted as electron acceptor for hydroxyl radical production to completely degrade Diazinon. Finally, the photocatalysis of the CoWO4/g-C3N4 was remained after three recycling runs implying that the heterojunction was relatively stable.