In-situ fabrication of reduced graphene oxide (rGO)/ZnO heterostructure: surface functional groups induced electrical properties

•An in-situ fabrication of reduced graphene oxide (rGO)/ZnO heterostructure via electrochemical deposition of ZnO directly on rGO was introduced;.•Rectifying I–V property of rGO/ZnO structure was obtained, indicating that rGO could be a promising p-type material for ZnO heterojunction;.•Based on Lerf-Klinowski model, C-sp2, hydroxyl and epoxy of rGO had been investigated to exploit the physical mechanism of the change in electrical property of rGO.