Silver ions (Ag+) are essential for living organisms; however, they are toxic at high concentrations. Herein, a photoelectrochemical (PEC) platform is constructed using TiO2 nanotube arrays (TiNTs) prepared by electrochemical anodization of electrode substrate, with high photocurrent response in visible-light region by coating PbS nanocrystals (NCs) through continuous chemical bath deposition (CBD) technique. Combining the low band-gap of PbS with the improved photogenerated electron-hole separation at PbS/TiO2 heterojunctions, the resulting PbS/TiNTs electrode possesses a highly improved PEC response under visible light. Owing to an efficient chemical replacement of Pb(II) in PbS by targeted Ag+ ions, the formed Ag2S components become the new recombination centers for charge carriers, leading to decreased PEC response. Based on photocurrent reduction, the PEC electrode demonstrated an excellent sensing ability for trace Ag+ in solution with a linear range of 5.0 × 10−3 ∼ 5.0 × 10−8 mol L−1 and a limit of detection reaching 1.5 × 10−8 M (S/N = 3). The semiconductor hybrid nanotubes-based photoelectrochemical platform provides a promising route to design highly sensitive and selective sensors for directly detecting ions or molecules.