Polydopamine/graphite sheet electrode for highly efficient electrocatalytic hydrogen peroxide generation and bisphenol A removal

Abstract

Electrocatalytic processes, are greatly limited by acid conditions during water/wastewater treatment, and lead to higher disposal costs. Herein, based on the principle of strong adhesion of invertebrate mussels, polydopamine with multiple functional groups was immobilized on graphite sheet electrodes for constructing the electrocatalytic system (GS-PDA), which achieved favorable stability in hydrogen peroxide (H2O2) yield and model pollutant Bisphenol A (BPA) removal at pH = 3–9. At natural pH (∼5.8), GS-PDA had a higher BPA removal efficiency with 113 % increase in degradation rate and an 1100 % increase in productivity of H2O2 than control group. O2 bubbling was the original contributor of oxidant and its two-electron reduction product (H2O2) had a significant contribution for BPA removal in GS-PDA. High pH (pH ≥ 5) increased the selectivity toward the four-electron oxygen reduction process (to H2O) in control group, while GS-PDA could inhibit this process, thus promoting the production of H2O2 from two-electron oxygen reduction process. Both hydroxyl radicals and singlet oxygen were effective in removing BPA and the former was the primary pathway. Furthermore, 18 dominant degradations were identified in GS-PDA by high resolution hybrid quadrupole time-of-flight mass spectrometer, and BPA degradation pathway was proposed. This work found a way to decrease the effects of pH on electrocatalytic purification of water and generation of H2O2, and provided a strategy for treating wastewater at neutral pH.