Arrays of titania nanotubes (TiO₂NTs) were developed by electrochemical anodization and doped with silver on their surface by photodeposition to achieve TiO₂NTs/Ag. It is found that only anatase TiO₂NTs were formed, with the preferential growth direction perpendicular to the titanium substrate, and with the length and diameter of ~2 µm and 90–120 nm, respectively. The presence of Ag on the surface of TiO₂NTs was also confirmed. The TiO₂NTs and TiO₂NTs/Ag were used as photocatalysts to decolorize the methylene blue (MB) aqueous solution. The photodegradation efficiency (PDE) is as high as 83% for TiO₂NTs and 98% for TiO₂NTs/Ag photocatalysts. This work focused on the investigation of the stability and recyclability of these photocatalysts in terms of efficiency and its physical origin by surface analysis using X-ray photoelectron spectroscopy (XPS). It is found that PDE diminishes from 83% to 76% in TiO₂NTs upon eight recycling runs and from 98% to 80% in TiO₂NTs/Ag upon six recycling runs. The XPS analysis revealed that the physical origin of diminishing efficiency is the carbon contamination on the surface of recycled TiO₂NTs and a combination of carbon contamination and Ag leaching in recycled TiO₂NTs/Ag.