Tandem Fields Facilitating Directional Carrier Migration in Van der Waals Heterojunction for Efficient Overall Piezo-Synthesis of H₂O₂.

Abstract

Piezo-synthesis of H₂O₂ utilizing sustainable mechanical energy as well as earth-abundant water and oxygen is a green, cost-effective, and promising approach. However, achieving simultaneous two-electron water oxidation reaction (2e^- WOR) and two-electron oxygen reduction reaction (2e^- ORR) faces huge challenges due to insufficient synergistic active sites and slow/messy carrier transfer. Herein, a novel 2D/2D van der Waals heterojunction consisting of BiOIO₃ and carbon nitride (BIO/CN) is elaborately designed for highly efficient overall H₂O₂ piezo-synthesis. Theoretical/experimental results reveal that a Z-scheme electron transfer is formed and facilitated by the tandem interfacial electric field and the bulk piezo-polarization field. On this basis, the carriers are efficiently separated while the oxidation/reduction capacity is preserved, thus providing the strong driving force for the 2e^- WOR and 2e^- ORR on BIO and CN, respectively. Furthermore, the kinetic and thermodynamic processes of WOR and ORR for H₂O₂ synthesis improve remarkably. Therefore, BIO/CN exhibits an excellent H₂O₂ yield of 259.8 µM within 30 min in pure water and air atmosphere (without any sacrificial agents and aeration). This study provides a new idea on strategically controlling electron transfer toward high-efficiency H₂O₂ piezo-synthesis and expands the avenue for developing effective environmental purification materials.