Synthesis, characterization, and photocatalytic performance of 2D/1D graphene/Ag–Ag2S hybrid nanocomposites

Abstract

The rational integration of different-dimensional nanostructures offers a powerful platform for engineering synergistic functionalities in photocatalysis. Herein, we report the controllable synthesis of novel 2D/1D graphene/silver–silver sulphide (Ag–Ag₂S) hybrid nanocomposites, wherein 1D Ag–Ag₂S nanowires (NWs) are uniformly anchored onto conductive graphene sheets, affording a hierarchical hybrid structure with tailored optoelectronic properties. Structural characterization via X-ray Diffraction (XRD) confirmed the coexistence of crystalline Ag, Ag₂S, and Ag₂O phases, evidencing both hybridization and partial oxidation during growth. Complementary Scanning Electron Microscopy (SEM) imaging revealed a homogeneous distribution of NWs across the graphene scaffold, ensuring maximized interfacial contact. Optical investigations demonstrated distinct band gap features (2.5 eV for Ag₂S, 3.8 eV for Ag NWs, and 4.6 eV for Ag₂O). In comparison, the composite exhibited dual transitions at 3.28 eV and 4.72 eV, attributed to interfacial charge transfer between Ag₂S and graphene, alongside enhanced plasmonic carrier dynamics. FTIR analyses further corroborated the hybrid composition, highlighting O–H and CC stretching vibrations of graphene, CO bands from surface PVP ligands, and Ag–S/Ag–O vibrational modes consistent with XRD assignments. Harnessing these tailored structural and electronic attributes, the graphene/Ag–Ag₂S heterostructures exhibited markedly superior photocatalytic activity toward methylene blue (MB) degradation, achieving a maximum efficiency of 89.55% under acidic conditions (pH 3) after 300 min of irradiation. Kinetic analysis revealed the highest rate constant (0.386 min⁻¹) for the graphene/Ag–Ag₂S nanocatalyst in acidic medium, surpassing both pristine Ag NWs and Ag–Ag₂S. This work highlights the potential of spatially engineered graphene-based heterostructures to modulate band structures, enhance charge carrier transport, and thereby improve selective photocatalytic dye removal.