Proton-coupled electron transfer activation of peroxydisulfate with phosphorylated zero-valent iron

Abstract

Heterogeneous peroxydisulfate (PDS) activation driven by conventional electron transfer (ET) is often frustrated by low thermodynamic driving force and sluggish kinetics. Herein, we propose a proton-coupled electron transfer (PCET) strategy of PDS activation, by utilizing ball-milled phosphorylated zero-valent iron (P-ZVIbm) as a PCET platform. P-ZVIbm efficiently activated PDS to produce SO4•− and •OH for rapid degradation of 4-chlorophenol in a wide pH range of 3.5–10.5, with rate constants 3–62 times those of the ZVIbm/PDS counterpart. PCET mechanism was evidenced by the pH dependent kinetics, kinetic isotope effect, and proton inventory study. The surface-bound phosphates offer flexible pendant protons (P-O-H) through hydrogen bonds, delocalizing electrons of peroxide O to polarize the O-O bond, thereby facilitating the ET from ZVI for O-O bond cleavage. The work demonstrates the superiority of PCET strategy for heterogeneous PDS activation, and shall guide the design of high-performance Fenton-like catalysts.