title: A half-reaction alternative to water oxidation: chloride oxidation to chlorine catalyzed by silver ion.
abstract: Chloride oxidation to chlorine is a potential alternative to water oxidation to oxygen as a solar fuels half-reaction. Ag(I) is potentially an oxidative catalyst but is inhibited by the high potentials for accessing the Ag(II/I) and Ag(III/II) couples. We report here that the complex ions AgCl2(-) and AgCl3(2-) form in concentrated Cl(-) solutions, avoiding AgCl precipitation and providing access to the higher oxidation states by delocalizing the oxidative charge over the Cl(-) ligands. Catalysis is homogeneous and occurs at high rates and low overpotentials (10 mV at the onset) with μM Ag(I). Catalysis is enhanced in D2O as solvent, with a significant H2O/D2O inverse kinetic isotope effect of 0.25. The results of computational studies suggest that Cl(-) oxidation occurs by 1e(-) oxidation of AgCl3(2-) to AgCl3(-) at a decreased potential, followed by Cl(-) coordination, presumably to form AgCl4(2-) as an intermediate. Adding a second Cl(-) results in "redox potential leveling", with further oxidation to {AgCl2(Cl2)}(-) followed by Cl2 release.
authors.affiliation: Shanghai Key Lab of Chemical Assessment and Sustainability, Department of Chemistry, Tongji University , Shanghai 200092, China.
authors.forename: Jialei
authors.initials: J
authors.lastname: Du
authors.forename: Zuofeng
authors.initials: Z
authors.lastname: Chen
authors.forename: Chuncheng
authors.initials: C
authors.lastname: Chen
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Meyer
mesh_terms: D002384:Catalysis; D002563:Cerium / Q000737:chemistry; D011232:Chemical Precipitation; D002712:Chlorides / Q000737:chemistry*; D002713:Chlorine / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D010084:Oxidation-Reduction; D012834:Silver / Q000737:chemistry*; D018030:Silver Compounds / Q000737:chemistry; D014867:Water / Q000737:chemistry*
chemical_list: D002712:Chlorides; D018030:Silver Compounds; D014867:Water; D002563:Cerium; D012834:Silver; D002713:Chlorine