Atomic H * -Mediated Electrochemical Reduction of Bromate by a Facile Ti/Pd@Mxene Filter Electrode

Abstract

Bromate (BrO3– ) is a common by-product of advanced oxidation water treatment processes. In this study, a catalyst combining MXene and Pd was synthesized to eliminate BrO3– by electrochemical reduction in flow-through mode. The fabricated Ti/Pd@MXene filter showed superior activity for BrO3– reduction, with a reaction rate constant (kobs) 2.1-fold greater than that of Ti/MXene filter. A satisfactory BrO3− removal performance by Ti/Pd@MXene filter was obtained at pH values of 5~7 with a current density of 1.0~2.5 mA·cm–2. The mechanism explored by quenching experiments and EPR analysis demonstrated that atomic hydrogen (H*)-mediated reduction was dominant in the Ti/Pd@MXene filter system and contributed to 84.2% of the BrO3− removal, which was greater than that of Ti (7.1%) and Ti/MXene (43.9%). DFT calculations revealed the introduction of Pd nanoparticles on MXene lowered the energy barrier for generating H* from OH*-H*, thus boosting H* generation. Furthermore, the Ti/Pd@MXene filter had favorable stability and applicability, and nearly 90% of BrO3− could be eliminated in different water matrices. Moreover, energy consumption of the Ti/Pd@MXene filter was more competitive than that previously reported (0.348 kWh·mmol−1), especially for high BrO3− removal (≥75%). This work highlighted an effective flow-through electrocatalytic filter to induce H*-mediated electrochemical reduction of BrO3−.

Keywords: Atomic hydrogen, Pd nanoparticles, flow-through, Indirect reduction