Interfacial polarization of boron carbon nitride gates nickel sites toward selective two-electron oxygen reduction.

Selective electrosynthesis of hydrogen peroxide (H2O2) via the two-electron oxygen reduction reaction (2e- ORR) requires a delicate balance between O2 activation and the suppression of OO bond cleavage in the *OOH intermediate. Here, a polarization-gated metal-BCN interface to direct ORR toward selective H2O2 production through soft OO bond activation was developed. By integrating Fe, Co, Ni, and Cu species into a polarized BCN matrix, we systematically elucidate how metal-dependent interfacial electronic structures govern the 2e- ORR pathway. Among them, Ni-BCN exhibits the optimal 2e- ORR performance, achieving 87% H2O2 selectivity at 0.5 V versus the reversible hydrogen electrode (RHE) and a Faradaic efficiency (FE) of 87% at -100 mA cm-2 in a flow cell, while maintaining stable operation for 100 h. Density functional theory (DFT) calculations reveal that the asymmetric polarization field of BCN electronically buffers the Ni sites, enabling moderate electron donation to O2, stabilizing end-on *OOH adsorption, facilitating H2O2 desorption, and suppressing the competitive OO bond cleavage pathway. This work identifies BCN-polarization-gated Ni sites as a selective interfacial motif for H2O2 and establishes a general strategy for governing oxygen reduction pathways through electronic polarization of the support induced by electrosynthesis.