​This study investigates the synergistic effects of combining Cu(II) ions with crystal facet-engineered titanium dioxide (TiO₂) to enhance its photocatalytic antimicrobial properties. Cu(II) is well-known for its strong antimicrobial effects, while TiO₂ has gained significant attention as a heterogeneous photocatalyst for practical water disinfection applications. Despite advancements in facet engineering of TiO₂, a significant gap remains in understanding photocatalytic microbial inactivation activity on different facets in the presence of Cu. This research explores how the redox reactions of Cu in TiO₂ are optimized through the electron-donating ability of the reductive facets under light illumination, aiming to leverage the complementary properties of Cu(II) and TiO₂ to create an efficient and sustainable disinfection system. The facet-dependent photocatalytic virucidal activities of TiO₂ nanotube arrays (TNAs) in the presence of Cu(II) under solar illumination are analyzed. Photo-electrochemical characterization demonstrates how different facet exposures affect charge separation and reactivity with Cu(II), enhancing the photocatalytic inactivation of MS2 bacteriophage. It is shown that TNAs with predominantly exposed {101} facets exhibit superior virucidal activity compared to those with {001} facets due to more effective interactions with Cu(II) and enhanced charge carrier dynamics. The role of Cu(II) as a pivotal co-catalyst in optimizing virucidal performance of TNAs is highlighted, marking a significant advancement in the application of photocatalytic materials for environmental disinfection and purification.