Oxygen-containing functional groups cooperate to boost electrochemical ORR selectivity to H2O2

Abstract

The electrocatalytic two-electron oxygen reduction reaction (2e⁻ ORR) for directly synthesizing H₂O₂ solution is expected to replace the conventional anthraquinone method. Oxygen doped carbon materials are promising as efficient electrocatalysts for the 2e⁻ ORR. Here, we developed a simple oxidation strategy to synthesize hydroxyl (–OH) and carboxyl (–COOH) co-modified carbon nanotubes (CNTs) for the 2e⁻ ORR. O-CNTs exhibit excellent H₂O₂ electrosynthesis performance in alkaline media, achieving a superior H₂O₂ yield (1.77 mol g_cat⁻¹ h⁻¹ in an H-type cell). Meanwhile, the O-CNTs achieve more than 90% faradaic efficiency (FE) over a wide potential range of 0.2–0.6 V vs. RHE. In situ attenuated total reflectance surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) confirms that O-CNTs could accelerate the generation of 2e⁻ ORR process intermediates (*OOH) for highly effective H₂O₂ production. In addition, in a three-electrode flow cell, O-CNTs exhibit superior activity and selectivity compared to other metal-free carbon materials in an alkaline electrolyte. Furthermore, comparison experiments and density functional theory (DFT) calculations confirmed that the co-modification of oxygen-containing functional groups is the main source of activity and selectivity of the electrochemical 2e⁻ ORR. This strategy tunes 2e⁻ ORR reactive sites and provides insights into the design of carbon-based catalysts for H₂O₂ electrosynthesis.