Atomic H⁎-mediated electrochemical reduction of bromate by a facile Ti/Pd@MXene filter electrode

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 compared with 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⁎ formation. 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⁻.