Deciphering co-catalytic mechanisms of potassium doped g-C₃N₄ in Fenton process

Conventional Fenton reaction for the pollutant removal is restricted by incomplete H₂O₂ decomposition due to the low efficient Fe(III)/Fe(II) cycle. In this study, the co-catalytic Fenton processes with g-C₃N₄ and the roles of potassium doping in the diverse mechanisms were comprehensively investigated. The degradation rate of enrofloxacin (ENR) in g-CN-3.9 %K/Fe(III)/H₂O₂ was 204 times higher than that in conventional Fenton reaction. This significant enhancement was ascribed to the readily formed complex between Fe(III) and K doped g-C₃N_4. The K doping facilitated the transfer of photoexcited e^- from g-CN-3.9 %K surface to Fe(III), leading to an accelerated Fe(III) reduction to Fe(II). In addition, this complex was coordinated and oxidized by H₂O₂, resulting in the formation of Fe(V) which quickly degraded ENR. Without K doping, on the other hand, only O₂ dominated the degradation of ENR in g-CN/Fe(III)/H₂O₂ due to the lack of Fe(III) complexation. This study provides a new perspective for regulating the transfer directions of the photoexcited e^- with K doping in g-C₃N₄/Fenton coupled catalytic system for water purification.