Directing electron flow via orbital-tailored heterojunctions toward selective H₂O₂ photosynthesis

This work addresses the fundamental dilemma between charge separation efficiency and surface reaction selectivity in heterogeneous photocatalysis through synergistic orbital engineering. By introducing Mo dopants and sulfur vacancies (V_S) into Zn₃In₂S₆, the localized electronic states of isolated V_S are transformed into delocalized charge channels via strong Mo 4d-S 3p orbital hybridization. This orbital-level modulation effectively suppresses charge recombination while optimizing the band structure for visible-light absorption. Coupled with in-situ grown Ni₄S₃, an interfacial Mo-S-Ni orbital bridge is constructed, which not only establishes a robust built-in electric field to direct electron flow toward Ni₄S₃ but also tailors the local coordination environment for selective two-electron oxygen reduction. The resulting heterojunction photocatalyst achieves an exceptional H₂O₂ production rate of 163.0 ± 2.1 μM h^-1 in pure water without any sacrificial agent. Notably, the H₂O₂ production rate of 252.1 ± 2.4 μM h^-1 is attained at a tetracycline hydrochloride (TC) concentration of 20 mg L^-1, 1.5 times higher than that in pure water. This study demonstrates that precise orbital coupling can integrate carrier dynamics management with reaction pathway control, providing a new design paradigm for noble metal-free, high-performance and multifunctional photocatalytic systems.