Regulating the electronic structure of iron sites in single-atom catalyst with interfacial chemical bond to enhance Fenton-like reaction.

Abstract

Single-atom Fenton-like catalysts have been proven to be more efficient compared with aggregated catalysts due to abundant active sites. However, the low reduction rate of Fe(III) to Fe(II) remained the rate-limiting step for single-atom Fenton-like catalysts. Herein, carbon nanotubes with electron-withdrawing groups (CNTs-COOH) were combined with a single-atom catalyst (FeSAC) to fabricate a novel catalyst (FeSAC/CNTs-COOH, FCC-x). The optimal FCC-5/H₂O₂ system exhibited a 6.8 times higher pseudo-first-order kinetic constant of SMX degradation than that in FeSAC/H₂O₂ system. Additionally, the FCC-5/H₂O₂ system could maintain high catalytic activity within a wide pH range (4-9). The results of experiments and calculations co-verified the formation of Fe-O bonds between CNTs-COOH and FeSAC, which significantly reduced the electronic density of Fe(III) sites and further accelerated Fe(III) reduction to Fe(II), hence boosted the Fenton reaction. Quenching experiments and EPR measurements confirmed that hydroxyl radicals (⋅OH) were the primary active species responsible for pollutant degradation. The degradation pathway and toxicity analysis indicated that FCC-5/H₂O₂ was an eco-friendly reaction system. This study will provide a promising method for enhancing the performance of single-atom Fenton-like catalysts and offers insights into the underlying mechanisms.