Efficient removal of Cl-DBPs by direct-indirect continuous hydrodechlorination reduction reaction on Ti₃C₂X₂ surface:...

Degradation of Chlorine-containing disinfection by-products(Cl-DBPs) on surface by electrocatalytic hydrodechlorination (EHDC) is considered a promising advanced water treatment method. Cl-DBPs have ecological toxicity and health risks so that it is urgent to degrade DBPs. We designed and verified the degradation performance of the EHDC of 18 kinds of DBPs (TAAs, TANs, TALs, TNMs, TAcAms, THMs) with different substituents led by the Ti₃C₂X₂(X = O/OH) system by the first-principles. On the surface of Ti₃C₂(OH)₂, DBPs react with atomic hydrogen (*H) by a direct-indirect continuous reduction mechanism to eliminate the Cl atom in turn. Dissociative adsorption of DBPs on the surface of Ti₃C₂(OH)₂ simultaneously realizes the first electron transfer step and forms H vacancy, which makes its electrocatalytic activity superior to that of Ti₃C₂O₂. Removing the six types of DBPs only needs to add -0.1 V of applied potential. In addition, we investigated the impact of substituents and chlorination degree on the reactivity of DBPs removal. The strong electron-withdrawing group is more conducive to the dechlorination reaction. Dehalogenation is much favorable in thermodynamics as the increase in chlorination degree. This study provides important insights and efficient catalysts for the degradation of DBPs and shows the potential of MXenes in eliminating chloride in water.