Abstract
Electrocatalytic H(2)O(2) production via the two-electron oxygen reduction reaction (ORR) is a highly sustainable alternative to industrial methods. To further optimize non-noble catalysts, we report an interfacial engineering strategy to stabilize the metastable P6(3)/mmc-La(2)O(3) phase on SrTiO(3). This symmetry evolution from the low-symmetry P3-m1 (trigonal) to the high-symmetry P6(3)/mmc (hexagonal) space group yields a composite with >95% H(2)O(2) selectivity. Mechanistic studies demonstrate that the symmetry-regulated interface optimizes *OOH conversion and suppresses O-O bond cleavage. This work offers a robust design principle for high-performance, noble-metal-free H(2)O(2) electrosynthesis.