Microfluidic Chip for the Photocatalytic Production of Active Chlorine

Active chlorine is the most powerful microbicidal reagent in swimming pools, potable water, hospitals, and medical surgeries. Its production mainly relies on reactive inorganic intermediates and electrochemical methods that involve undesired waste products and high energy as well as material costs. In this study, we fabricated a low-cost chip based on sputter-coated thin films of silver (Ag) that acted as recyclable and effective photoelectrode for the photocatalytic production of active chlorine (HOCl) from aqueous media and artificial sunlight. The photoelectrode was electrochemically activated to AgCl at low overpotentials between 0.2 and 0.4 V vs Ag|AgCl (3 M KCl) and photocatalytically reduced to Ag⁰ for 15 consecutive cycles, showing the electrode still being active. However, because of poor adhesion properties on the selected substrates, degradation effects were observed over time. Furthermore, the Ag@AgCl photoelectrode was integrated into a microfluidic chip, and we showed for the first time a light-driven microfluidic chip generating a constant stream of active chlorine.