Interfacial Field Screening Governs Tribocatalysis in Nb-Doped SrTiO3

Harnessing contact electrification to drive redox reactions offers a promising, illumination-independent route for wastewater remediation. However, the interfacial mechanisms governing tribocatalytic efficiency remain unclear. Here, Nb-doped SrTiO₃ (0.25–2 mol %) was systematically investigated under Tribo-, Light-, Dark-, and combined Tribo-Light conditions to elucidate the role of electronic structure and field screening on performance. Mott–Schottky and Kelvin probe force microscopy (KPFM) analyses reveal that increasing Nb content raises the Fermi level and compresses the Debye screening length (λ D ) from ≈ 6 nm (0.25 % Nb) to ≈ 4.5 nm (2 % Nb). EIS confirms this shortening through reduced space-charge resistance, while zeta-potential measurements show consistently moderate negative values (≈ –25 to –30 mV), excluding adsorbed species as the dominant factor. An optimal λ D window of 5.5–6.0 nm at 0.25–0.5 % Nb balances donor concentration and interfacial field penetration, enabling efficient electron extraction and radical generation. Consequently, 0.25 % Nb–SrTiO₃ achieves 90 % RhB degradation in 24 h (Tribo-only) and complete MB removal within 2 h (Tribo-Light), whereas 2 % Nb over-screens the surface field and suppresses reactivity. These findings identify the Debye length as a quantitative descriptor for tribocatalytic design, providing a mechanistic basis for engineering high-efficiency, bias-free catalysts for environmental remediation.