S–Modified MXene as a Catalyst for Accelerated Tetracycline Hydrochloride Electrocatalytic Degradation via ·OH and Active Chlorine Triggering Promotion

S–modified MXene (Ti3C2Tx@S–5) was prepared to improve the catalytic activity of MXene in the electrocatalytic degradation of tetracycline hydrochloride (TC). Here, S groups in the form of Ti–S and S–O species were anchored onto MXene, resulting in superior conductivity and surface activity. Ti3C2Tx@S–5 exhibited an excellent performance of 100% TC degradation under the conditions of 25 °C, a pH of 6, a TC concentration of 10 mg L−1, and an applied current of 20 mA. Radical quenching and EPR analyses revealed that ·O2− and 1O2 played dominant roles in Ti3C2Tx@S–5 and Ti3C2Tx systems. Furthermore, S modification promoted the triggering of ·OH and active chlorine, which contributed to the acceleration of TC degradation. The involvement of these active substances in degradation pathways was further proven. This research advances the S modification of MXene and improves TC degradation by promoting the triggering of ·OH and active chlorine, broadening the applicability of MXene material.