Covalency competition triggers Fe-Co synergistic catalysis for boosted Fenton-like reactions

Fe-Co based oxides demonstrate excellent Fenton-like catalytic activity, but the intrinsic mechanism of Fe-Co synergy remains elusive. Here, we uncover the influence of covalency competition between Fe and Co on catalytic behaviors in peroxymonosulfate (PMS) activation. Theoretical and experimental analysis reveals that higher electron delocalization of octahedral Co (CoOh)-O unit and lower electron delocalization of FeOh-O unit boost electron transfer between Co and O species and transformation of SO5•− towards surface-bounded and free SO4•− instead of 1O2. With favorable covalency competition, electron transfer capability, active oxidizing species, (Co0.8Fe0.2)Oh-O unit exhibits superior activity with rate constant of 0.27 min−1, 254.7, 37.5 and 2.2 times of that in PMS, FeOh-O unit/PMS and CoOh-O unit/PMS systems, respectively, outperforming all the reported Fe-Co based oxides in removal of refractory pollutants. The improved insights into the origin of Fe-Co synergy advance the rational development of highly efficient catalytic oxidation systems for water decontamination.