Pure Zinc Oxide (ZnO) nanoparticles (NPs) and gold (Au) decorated (Au-ZnO) hetero-nanostructures were synthesized using green-synthesis method employing pecan nuts (Carya illinoinensis) leaves extract as reducing agent. The structural and optical properties studied by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX), High-resolution transmission electron microscopy (HRTEM) and UV-vis spectrophotometer (UV-vis). Structural modification with the introduction of Au in ZnO have been confirmed by the XRD and TEM results. UV data confirmed the decrease in Au-ZnO energy band-gap Eg value, which validates the formation of hetero-structure. The modulation of energy band-gap causes visible light absorption and hence enhances the photodegradation activity of Au-ZnO. Photocatalytic activity was carried-out by degradation of RhB dye under UV light irradiation in aqueous solution. The maximum degradation of 95 % was obtained during the time of 180 min for the basic pH of the dye. The Enhanced degradation in Au-ZnO as compared with bare ZnO NPs, was attributed to Au, which controls the amount of electron and suppress electron-hole ratio at ZnO surface. In the recycling study of the Au-ZnO Photocatalyst, the hetero-structure showed good stability up to five cycles.