Efficient co-catalysis of Ti2C MXene in Fenton system: Promotion of Fe3+/Fe2+ cycling

• Ti 2 C MXenes exhibited excellent co-catalysis effect in Fenton system; • Ultrafast reduction of Fe 3+ was achieved with Ti 2 C (10%/HF) under neutral condition; • Ti 2 C MXenes reduced Fe 3+ by breaking Ti-C bond and Ti (II) valence transition. In this study, the Ti 2 C MXenes were prepared by using acid etching under different etching conditions. Their co-catalytic performances in Fenton system were evaluated by degrading the typical antibiotic SMX with the employment of Fe 3+ . The results showed that the Ti 2 C MXene etched by 10 % HF for 12 h (Ti 2 C (10%/HF) ) can effectively promote the reduction of Fe 3+ in heterogeneous Fenton system. Under neutral conditions, the Ti 2 C (10%/HF) /Fe 3+ /H 2 O 2 system achieved 99.2 % SMX degradation within 30 min, with the reaction rate constant 17.7 times and 1.4 ∼ 6.2 times faster than that in Fe 3+ /H 2 O 2 and other Ti 2 C MXenes/Fe 3+ /H 2 O 2 systems. Both the concentration measurements of Fe 2+ and Fe 2p XPS results confirmed the excellent generation of Fe 2+ in the Ti 2 C (10%/HF) /Fe 3+ /H 2 O 2 system. The density functional theory (DFT), cyclic voltammetry (CV) and electrochemical impedance spectra (EIS) results showed that Ti 2 C (10%/HF) had excellent adsorption, charge mediation, electron transfer and diffusion properties. Meanwhile, XPS analysis showed that reduction sites (Ti (II) and Ti-C) had been produced on Ti 2 C (10%/HF) during the etching process. These properties might have enhanced the Fe 3+ to interact with Ti 2 C (10%/HF) effectively, allowing rapid reduction of Fe 3+ to Fe 2+ . The generated Fe 2+ was diffused into the solution to activate H 2 O 2 for the production of reactive oxygen species (ROS), promoting the efficient degradation of SMX in the Ti 2 C (10%/HF) /Fe 3+ /H 2 O 2 system. This study reveals a new pathway for facilitating the Fe 3+ /Fe 2+ cycling under neutral condition, and provides a promising co-catalyst for enhancing the performance of Fenton system.