A cuprous oxide (Cu2O) nanoparticles modified Pt rotating ring-disk electrode (RRDE) was successfully fabricated, and the electrocatalytic determination of p-nitrophenol (PNP) using this electrode was developed. Cu2O nanoparticles were obtained by reducing the copper-citrate complex with hydrazine hydrate (N2H4 center dot H2O) in a template-free process. The hydrodynamic differential pulse voltammetry (HDPV) technique was applied for in situ monitor the photoelectrochemical behavior of PNP under visible light using nano-Cu2O modified Pt RRDE as working electrode. PNP undergoes photoelectrocatalytic degradation on nano-Cu2O modified disk to give electroactive p-hydroxylamino phenol species which is compulsive transported and can only be detected at ring electrode at around 0.05V with oxidation signal. The effects of illumination time, applied bias potential, rotation rates and pH of the reaction medium have been discussed. Under optimized conditions for electrocatalytic determination, the anodic current is linear with PNP concentration in the range of 1.0 x 10(-5) to 1.0 x 10(-3) M, with a detection limit of 1.0 x 10(-7) M and good precision (RSD =2.8%, n = 10). The detection limit could be improved to 1.0 x 10(-8) M by given illumination time. The proposed nano-Cu2O modified RRDE can be potentially applied for electrochemical detection of p-nitrophenol. And it also indicated that modified RRDE technique is a promising way for photoelecrocatalytic degradation and mechanism analysis of organic pollutants. (C) 2010 Elsevier Ltd. All rights reserved.