Sunlight-Driven Generation of Hypochlorous Acid on Plasmonic Au/AgCl Catalysts in Aerated Chloride Solution

[Image: see text] HClO is typically manufactured from Cl(2) gas generated by the electrochemical oxidation of Cl(–) using considerable electrical energy with a large concomitant emission of CO(2). Therefore, renewable energy-driven HClO generation is desirable. In this study, we developed a strategy for stable HClO generation by sunlight irradiation of a plasmonic Au/AgCl photocatalyst in an aerated Cl(–) solution at ambient temperature. Plasmon-activated Au particles by visible light generate hot electrons, which are consumed by O(2) reduction, and hot holes, which oxidize the lattice Cl(–) of AgCl adjacent to the Au particles. The formed Cl(2) is disproportionated to afford HClO, and the removed lattice Cl(–) are compensated by the Cl(–) in the solution, thus promoting a catalytic HClO generation cycle. A solar-to-HClO conversion efficiency of ∼0.03% was achieved by simulated sunlight irradiation, where the resultant solution contained >38 ppm (>0.73 mM) of HClO and exhibited bactericidal and bleaching activities. The strategy based on the Cl(–) oxidation/compensation cycles will pave the way for sunlight-driven clean, sustainable HClO generation.