Hydrogen Peroxide Electrosynthesis in a Strong Acidic Environment Using Cationic Surfactants

Abstract

The two-electron oxygen reduction reaction (2e − -ORR) can be exploited for green production of hydrogen peroxide (H 2 O 2 ), 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 H 2 O 2 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 H 2 O 2 Faradaic efficiency (FE) was improved from 12% to 95% H 2 O 2 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 O 2 gas transport and its hydrophobic tail could displace local protons under applied negative potentials during catalysis, which are responsible for the improved H 2 O 2 selectivity in strong acids.