Silver photodeposition modulated by defect-interface electrostatic coupling in two-dimensional semiconductor...

Two-dimensional (2D) semiconductor nanosheets (NSs) provide an atomically precise platform for photocatalysis. In this study, we utilize silver (Ag) photodeposition (PD) to spatially resolve the photocatalytic activity of titania NSs, uncovering dense Ag deposition distinct from that observed in conventional titania-based nanomaterials and other ultrathin materials. The Ag nucleation is likely initiated at intrinsic Ti⁴⁺ vacancy sites distributed within the 2D structure, and the growth appears to be primarily governed by interfacial states. Specifically, annealing at 400 °C promotes the decomposition of tetra-n-butylammonium cations, possibly producing smaller ionic species, such as nitrogen-containing fragments and/or H₃O⁺ at the monolayer-substrate interface. These species could passivate Ti⁴⁺ vacancy sites, thereby suppressing Ag growth on monolayer titania NSs. Without annealing, larger C₄N⁺ species with lower charge density remain more abundant at the interface and could interact weakly with the active sites, allowing Ag PD to extend by several nanometers. This work provides a conceptual basis for defect-interface engineering of dense and tunable metal photodeposition on atomically thin semiconductor platforms.