Novel active chlorine based-mechanism for 1O2-dominated tetracycline hydrochloride electrocatalytic oxidation over N-doped MXene

Chloride ions (Cl−) as electrolyte contribute remarkably to electrocatalytic oxidation because of the by-production of active chlorine. Experiment and theoretical calculation were proposed to clarify the contribution of Cl− to TC degradation, the generation and contribution mechanism of active chlorine, and the mutual transformation of active species. DFT results showed the favorable adsorption and conversion of Cl− on Ti-N, Ti-O-N, and Ti-N-O sites of Ti3C2Tx@N-0.1, thereby facilitating the generation of active chlorine and improving the TC degradation. The limited effect of direct electrocatalytic degradation (leading to O2– and 1O2 accumulation) and active chlorine (e.g., HClO) oxidation was proved by quenching, EPR, and qualification test of active species. The secondary and dominant production of 1O2 from active chlorine conversion was greatly improved in Ti3C2Tx@N-0.1/electrocatalysis system and played a crucial role in TC removal. The mutual transformation of OH, O2–, and 1O2 from direct electrocatalysis and secondary active chlorine conversion also enriched the TC removal mechanism. This research provides novel insights into the influence of active chlorine on electrocatalytic oxidation and the underlying mechanism.