The 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. Whereas, Oxygen doped carbon materials are promising as efficient electrocatalysts for 2e− ORR. Here, we developed a simple oxidation strategy to synthesize hydroxyl (-OH) and carboxyl (-COOH) co-modified carbon nanotube (CNTs) for 2e− ORR. O-CNTs exhibits excellent H2O2 electrosynthesis performance in alkaline media, achieving superior H2O2 yield (1.77 mol·gcat−1·h−1 in H-type cell). Meanwhile, the O-CNTs achieve more than 90% Faraday efficiency (FE) over a wide potential of 0.2 ~ 0.6 V vs. RHE. In situ attenuated total reflection 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 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 electrochemical 2e− ORR. This strategy tunes 2e− ORR reactive sites and provides insights into the design of carbon-based catalysts for H2O2 electrosynthesis.