The complex heterogeneous Fenton reactivity of transition metal-doped ferrihydrite: Insight from the structural variation and pathway of H2O2 activation

Doping transition metal into ferrihydrite (Fh) may significantly affect its structure and Fenton reactivity. The comparative study of Fh and M(II)-Fh (M = Cu, Co, or Mn), for the first time, reveals that doping metal ions can alter the property and content of oxygen vacancy (OVs) and the oxidation potential of Fh, which subsequently affects H2O2 decomposition, HO. generation, and Fenton reactivity of the catalysts. The overall Fenton activity of the samples in decomposing bisphenol A decreases in the order Cu-Fh > Fh > Co-Fh > Mn-Fh. In specific, Cu-Fh is the most efficient catalyst as it has the lowest energy barrier for decomposing H2O2 into HO. at OVs sites and the highest oxidation potential (benefiting the reduction of Fe(III) to Fe(II) by H2O2). Our findings show the complex heterogeneous Fenton reactivity of M-Fh, and doping can be an efficient strategy for achieving highly efficient Fenton catalysts.