A synergistic boost of photo-activity of ZnO for photocatalytic degradation of methylene blue by Ag decoration and Fe doping

•Fe-doped Ag-ZnO was synthesized by a facile polymer network gel method.•The optimal catalytic activity can be obtained by modulating the Fe and Ag proportion.•The transformation from Fe2+ to Fe3+ is observed by increasing the Fe concentration.•High content of surface active Fe2+ seems to be favorable for photocatalytic reaction.