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Nickel-polypyrrole co-modified ZnO nano-composites (Ni-ZnO/Ppy) were synthesized by two methods, metal impregnation of nickel (Ni) and In-situ chemical polymerization of polypyrrole (Ppy) on ZnO nano-particles. The crystal size, band gap energy and bond structure of as-synthesized nano-composites were investigated by using x-ray diffraction(XRD),UV-Vis and Fourier transform infrared (FT-IR) spectroscopic techniques respectively. Photo-catalytic degradation efficiency of synthesized photo-catalysts was investigated on p-nitrophenol dyes under solar irradiations and Co-doped photo-catalysts shows better catalytic degradation efficiency than both ZnO and Ni-ZnO nano-particles. Ni-ZnO/Ppy photo-catalysts effectively degraded 96.04% of p-nitrophenol dye on 180 minute visible light irradiation. Highest photo-catalytic activity of Ni-ZnO/Ppy nano-composites over ZnO photo-catalysts was attributed due dopants to the lower rate of recombination of the photo generated electrons- holes as well as its lower crystal size and band gap energy. The photo-catalytic degradation of p-nitrophenol kinetically follows pseudo first-order reactions for Ni-ZnO/Ppy photo-catalysts.