Advancing Microbial Electrochemical H₂O₂ Synthesis by Tailoring the Surface Chemistry of Stereolithography-Derived 3D Pyrolytic Carbon Electrodes

Microbial electrosynthesis of H₂O₂ offers an economical and eco-friendly alternative to the costly and environmentally detrimental anthraquinone process. Three-dimensional (3D) electrodes fabricated through additive manufacturing demonstrate significant advantages over carbon electrodes with two-dimensional (2D) surfaces in microbial electrosynthesis of H₂O₂. Nevertheless, the presence of oxygen-containing free acidic groups on the prototype electrode surface imparts hydrophilic properties to the electrode, which affects the efficiency of the two-electron oxygen reduction reaction for H₂O₂ generation. In this study, we elucidated that the efficiency of microbial H₂O₂ synthesis is markedly enhanced by utilizing oxygen-free 3D electrodes produced via additive manufacturing techniques followed by surface modifications to eradicate oxygen-containing functional groups. These oxygen-free 3D electrodes exhibit superior hydrophobicity compared to traditional carbon electrodes with 2D surfaces and their 3D printed analogues. The oxygen-free 3D electrode is capable of generating up to 130.2 mg L^-1 of H₂O₂ within a 6-h time frame, which is 2.4 to 13.6 times more effective than conventional electrodes (such as graphite plates) and pristine 3D printed electrodes. Additionally, the reusability of the oxygen-free 3D electrode underscores its practical viability for large-scale applications. Furthermore, this investigation explored the role of the oxygen-free 3D electrode in the bioelectro-Fenton process, affirming its efficacy as a tertiary treatment technology for the elimination of micropollutants. This dual functionality accentuates the versatility of the oxygen-free 3D electrode in facilitating both the synthesis of valuable chemicals and advancing environmental remediation. This research introduces an innovative electrode design that fosters efficient and sustainable H₂O₂ synthesis while concurrently enabling subsequent environmental restoration.