Highly efficient tribocatalytic hydrogen peroxide production over Fe₂O₃ nanoparticles and the reaction pathways

Tribocatalysis offers a promising green and safe approach for hydrogen peroxide (H₂O₂) production, but the environmentally friendly and low-cost tribocatalysts are still lacking, along with the reaction pathway under debate. Herein, Fe₂O₃ nanoparticles prepared by a hydrothermal process exhibit excellent tribocatalytic H₂O₂ production performance, and the reliable reaction pathways are revealed. The Fe₂O₃ nanoparticles achieve an H₂O₂ yield of 3269 μmol·g^-1·h^-1 in pure water and air without any sacrificial agents, as well as consistent performance during cycles, and the amount reaches 14,861 μmol·g^-1 in 5 h under ultrasonic vibration. The acquired H₂O₂ yield outperforms most recently reported tribocatalysts and piezocatalysts. Furthermore, the tribocatalytic system can be used for highly efficient treatment of mixed dye wastewater. Scavenger experiments combined with pH value monitoring are first designed to reveal the detailed H₂O₂ production reaction pathways, in which the indirect two-electron (2e^-) oxygen reduction reaction (ORR) is the dominant pathway, while the 4e^- water oxidation reaction (WOR) and 2e^- WOR provide O₂ and H⁺ to boost the 2e^- ORR. This study reveals the effectiveness of monitoring the pH value changes in the reaction solution for exploring the H₂O₂ production reaction pathway, provides an effective approach for exploring the reaction pathway of hydroxyl radical, and the established approaches can also be applied in photocatalytic, piezocatalytic, and flexocatalytic H₂O₂ production processes.