Dual-metal synergy and interfacial electric field engineering in CNNS/Ni-Ag heterostructure for sacrificial agent-free in-situ H₂O₂-enabled self-photo-driven Fenton degradation

In this work, a composite photocatalyst based on graphitic carbon nitride nanosheets (CNNS) co-deposition with Ni and Ag was developed without employing any sacrificial agent to simultaneously achieve photocatalytic H₂O₂ production and photo-self-Fenton degradation of metronidazole. The experimental characterization using the transient photovoltage and Kelvin probe in combination with density functional theory (DFT) calculations reveals that an interfacial built-in electric field efficiently drives the directional migration of photogenerated electrons from CNNS and hot electrons induced by localized surface plasmon resonance (LSPR) from Ag sites toward Ni sites, remarkably suppressing charge recombination. While being the primary electron-trapping center, Ni facilitates O₂ adsorption and two-electron reduction on Ni/Ag bimetallic sites. Under optimal conditions, the catalyst achieves an H₂O₂ generation rate of 681.2 μmol g⁻¹ h⁻¹ in pure water, which afterward increases to 1541.3 μmol g⁻¹ h⁻¹ upon the addition of isopropanol (IPA). The in-situ-generated H₂O₂ is subsequently harnessed to construct a self-driven photo-Fenton system capable of efficiently degrading 92.9 % of metronidazole (20 mg L⁻¹) within 60 min. This work offers a new route for designing photocatalysts that couple in-situ H₂O₂ generation with advanced oxidation processes for environmental remediation.