Hydrogen Peroxide Electrosynthesis in a Strong Acidic Environment Using Cationic Surfactants

The two-electron oxygen reduction reaction (2e^--ORR) can be exploited for green production of hydrogen peroxide (H₂O₂), but it still suffers from low selectivity in an acidic electrolyte when using non-noble metal catalysts. Here, inspired by biology, we demonstrate a strategy that exploits the micellization of surfactant molecules to promote the H₂O₂ selectivity of a low-cost carbon black catalyst in strong acid electrolytes. The surfactants near the electrode surface increase the oxygen solubility and transportation, and they provide a shielding effect that displaces protons from the electric double layer (EDL). Compared with the case of a pure acidic electrolyte, we find that, when a small number of surfactant molecules were added to the acid, the H₂O₂ Faradaic efficiency (FE) was improved from 12% to 95% H₂O₂ under 200 mA cm^-2, suggesting an 8-fold improvement. Our in situ surface enhanced Raman spectroscopy (SERS) and optical microscopy (OM) studies suggest that, while the added surfactant reduces the electrode's hydrophobicity, its micelle formation could promote the O₂ gas transport and its hydrophobic tail could displace local protons under applied negative potentials during catalysis, which are responsible for the improved H₂O₂ selectivity in strong acids.