Crystal-facet-dependent piezo-phototronic effect steering reaction pathway switching for efficient H₂O₂ production...

The efficiency of photocatalytic H₂O₂ production is often hampered by sluggish reaction kinetics and unfavorable thermodynamic potentials, especially when relying on the water oxidation reaction (WOR) pathway. This study demonstrates that the piezo-phototronic effect can be harnessed to dynamically steer the reaction pathway toward the more efficient two-electron oxygen reduction reaction (2e^- ORR). We designed a ZnO-TiO₂ heterojunction system with tailored exposure of polar (100) facets by controlling the growth orientation of ZnO nanorods. The facet-dependent piezoelectric potential effectively remodulates the interfacial band alignment of the Type-II heterojunction, leading to dramatically enhanced bulk charge separation and interfacial transfer. This optimized charge flow consequently lowers the thermodynamic barrier for O₂ activation and favors the 2e^- ORR pathway. As a result, an exceptional H₂O₂ production rate of 1.43 mmol·g^-1·h^-1 in pure water without any sacrificial agents or noble metals was achieved, representing a 420 % enhancement over pristine ZnO. The combination of multi-physics simulations, density of states calculations, and in situ characterization techniques unravels how the facet-governed piezoelectric polarization governs the band displacement and charge separation dynamics. Isotope tracing, and theoretical calculations collectively reveal a fundamental shift in the H₂O₂ formation mechanism: from a water-oxidation-dominated process to a piezo-phototronic-effect-driven 2e^- ORR pathway. This work provides a profound insight into the crystal-facet-dependent piezo-phototronic effect and establishes a universal strain-mediated strategy for manipulating catalytic selectivity in renewable energy conversions.