Hydrogen Radical Enabling Industrial-Level Oxygen Electroreduction to Hydrogen Peroxide

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Electrochemical synthesis of hydrogen peroxide (H2O2) using renewable electricity offers a sustainable alternative to the energy-intensive industrial autoxidation process.
• The two-electron oxygen reduction reaction (2e-ORR) mechanism, particularly the role of local protons, remains incompletely understood, hindering optimization.
• Developing efficient electrocatalysts is crucial for advancing sustainable H2O2 production.

Purpose of the Study:

• To investigate the influence of local proton availability on the kinetics and selectivity of the 2e-ORR.
• To elucidate the function of hydrogen-associated intermediates in the 2e-ORR mechanism.
• To design and evaluate a cooperative electrode material for enhanced H2O2 synthesis.

Main Methods:

• Rationally designed a cooperative electrode material: cobalt (II) clusters embedded onto oxidized carbon nanotube composites (Co-OCNT).
• Investigated the 2e-ORR using electrochemical synthesis powered by renewable electricity.
• Analyzed reaction kinetics, selectivity, and intermediate pathways using the Co-OCNT material.

Main Results:

• Confirmed a 2e-ORR process involving hydrogen radical transfer, where local proton availability dictates reaction performance.
• The Co-OCNT electrode demonstrated superior kinetics and selectivity, achieving an H2O2 production rate of ~40.6 mol gcat−1 h−1 and 90% faradaic efficiency at 300 mA cm−2.
• Oxidized carbon nanotube sites promoted proton production, while cobalt sites facilitated ORR intermediate formation, showcasing cooperative dual-active sites.

Conclusions:

• High local proton availability and cooperative dual-active sites in the Co-OCNT material significantly enhance 2e-ORR performance for H2O2 synthesis.
• The developed material shows promise for sustainable and efficient electrochemical H2O2 production.
• Cascading the 2e-ORR with electro-Fenton processes demonstrated high selectivity (97%) for oxalic acid production from ethylene glycol valorization.