Mechanistic Insights into Surfactant-Modulated Electrode–Electrolyte Interface for Steering H₂O₂ Electrosynthesis

Abstract

Electrocatalytic reactions taking place at the electrified electrode−electrolyte interface involve processes of proton-coupled electron transfer. Interfacial protons are delivered to the electrode surface via a H 2 Odominated hydrogen-bond network. Less efforts are made to regulate the interfacial proton transfer from the perspective of interfacial hydrogen-bond network. Here, we present quaternary ammonium salt cationic surfactants as electrolyte additives for enhancing the H 2 O 2 selectivity of the oxygen reduction reaction (ORR). Through in situ vibrational spectroscopy and molecular dynamics calculation, it is revealed that the surfactants are irreversibly adsorbed on the electrode surface in response to a given bias potential range, leading to the weakening of the interfacial hydrogen-bond network. This decreases interfacial proton transfer kinetics, particularly at high bias potentials, thus suppressing the 4-electron ORR pathway and achieving a highly selective 2-electron pathway toward H 2 O 2 . These results highlight the opportunity for steering H 2 O-involved electrochemical reactions via modulating the interfacial hydrogen-bond network.

Surfactant Directionally Assembled at the Electrode‐Electrolyte Interface for Facilitating Electrocatalytic Aldehyde Hydrogenation

“…Previous studies have evidenced that there are three types of OÀ H stretching vibration patterns in water. [44][45][46][47] The high wavenumber band can be ascribed to isolated water molecules without hydrogen bonds (weak hydrogen-bonded water). The middle and low wavenumber bands correspond to water molecules with one to three hydrogen bonds (analogous to asymmetrically hydrogenbonded water molecules with cationic hydration shells) and water molecules with four hydrogen bonds (analogous to bulk or ice-like water with symmetrically hydrogen-bonded water), respectively.…”