Hierarchical MoS2 nanosheets on flexible carbon felt as an efficient flow-through electrode for dechlorination

Abstract

MoS₂, a layered transition metal dichalcogenide, is well-known as an efficient catalyst for the hydrogen evolution reaction. For the first time, we show that MoS₂ is also a promising electrocatalyst for reductive dehalogenation of chloro-substituted carboxylic acids in water. MoS₂ nanosheets were grown directly on flexible/soft carbon felt using a facile hydrothermal method. The MoS₂ nanosheet loaded carbon felt was used as flow-through electrode for reductive dechlorination of trichloroacetic acid under environmentally relevant conditions resulting in a much more efficient process than using metal electrodes. Atomic hydrogen produced from water reduction at the MoS₂ surface can be exploited to accomplish a complete dehalogenation, yet with a dramatic drop in the Faradaic efficiency due to the concomitant dihydrogen evolution. Doping of the MoS₂ catalyst with transition metals resulted in an increase in the Faradaic efficiency as well as the complete dechlorination of trichloroacetic acid to acetic acid. The edge sites of MoS₂ are believed to be responsible for the indirect dechlorination involving atomic hydrogen. With the cobalt doped MoS₂ catalyst, 100% full dechlorination was accomplished at an applied potential of −1.1 V vs. Ag/AgCl using a flow rate of 1 mL min⁻¹. The catalyst synthesis, electrode preparation, and setup of the electrochemical flow cell are straightforward and readily up-scaled, demonstrating the potential of this methodology in practical applications.