Non-radical photoelectrochemical production of free chlorine from diluted chloride solutions on BiVO4

Free chlorine (FC) species are important oxidants for organic synthesis and environmental remediation. However, due to competitive water oxidation, it’s hard to obtain satisfied photoelectrochemical Faradic efficiency (FE) of FC via energetically unfavorable •Cl intermediate. Herein, we developed a non-radical strategy to realize efficient and stable FC production. High FE (86.2 %), high partial photocurrent density (2.8 mA/cm2) and excellent stability were achieved even under the conditions of diluted Cl (0.1 M) and neutral pH. Furthermore, compared with BVO, BVO@AgCl exhibited multi-fold faster rates for chlorine-mediated oxidations of styrene and arsenite with superior FEs (90.0 % vs. 59.4 %; 89.3 % vs. 47.3 %). Mechanistically, photogenerated holes are accumulated at AgCl sites (Cl+). FC is catalytically produced from the nucleophilic attack of Cl to Cl+, which bypasses •Cl intermediate and energetically outcompetes water oxidation. This work provides promising photoelectrochemical systems for highly efficient and stable production of FC, promoting high-value-added chemical synthesis and water treatment. [Display omitted] •A non-radical photoelectrochemical strategy to realize the efficient and stable FC production, by modifying BiVO4 (BVO) photoanodes with AgCl sites (BVO@AgCl).•Relative to •Cl pathway on BVO, photogenerated holes are accumulated at AgCl sites, and FC is catalytically produced from the nucleophilic attack of Cl to the oxidized AgCl sites (Cl+) in a non-radical manner, which is energetically outcompetes water oxidation to •OH.