Hydrogen peroxide (H
2O
2) is an essential chemical utilized in disinfection, water treatment, chemical synthesis, and the paper and pulp manufacturing industry. Our group produces H
2O
2 via the two-electron oxygen reduction reaction (2e
--ORR), which utilizes electricity from renewable resources. This technique has several advantages over the current industrial method for H
2O
2 synthesis, the anthraquinone process. No organic waste is produced; the infrastructure is not limited to a centralized location, reducing transportation costs; and the emissions are clean. Much of the H
2O
2 literature has focused on electrosynthesis in alkaline electrolytes as the higher pH environment favors the ORR over the hydrogen evolution reaction (HER). However, the implementation of H
2O
2 electrosynthesis in an acidic environment could help with the commercialization of practical H
2O
2 electrolyzers due to the superior stability of the
in-situ generated H
2O
2 in low pH solutions and the compatibility with commercially-available proton-exchange membranes (PEMs). In order to exploit both high selectivity toward H
2O
2 product and high stability of the generated H
2O
2, we introduced cationic surfactants to a strongly acidic solution, which increased the H
2O
2 selectivity at low pH from 12% to 95% Faradaic efficiency (FE) under a current density of 200 mA cm
-2. We employed
in-situ surface enhanced Raman spectroscopy (SERS) and optical microscopy (OM) in order to understand the behavior of the electrode-electrolyte interface under electrolysis operating conditions. The results from our experiments demonstrate that the surfactant molecules become attracted to the electrode surface, likely displacing protons at the electrode-electrolyte interface, and thus promoting the ORR over HER. We also detected micelles in solution under OM imaging, which can facilitate O
2 gas transport to the electrode surface, further favoring ORR conditions to produce H
2O
2.
Figure 1. Schematic portraying hypothetical electric double layer at cathode interface (a.) without CTAB and (b.) with CTAB.
