Facile Low-Temperature Solid-Phase Synthesis of Cubic SnS for Enhanced Photocatalytic Performance

This study employed tin hydroxysulfate and thiourea as raw materials to successfully prepare single-phase SnS and SnS/SnO composite photocatalysts with unique microstructures via a simple low-temperature solid-state reaction. X-ray diffraction (XRD) analysis revealed that the phase composition of the products was strongly dependent on the thiourea content: an appropriate amount favored the formation of single-phase cubic SnS, while excess thiourea induced the formation of a minor SnO phase. Characterization by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that the materials possessed a multi-scale heterojunction structure, composed of numerous SnS ultrafine nanoparticles (<5 nm) and SnS/SnO crystalline grains (20–30 nm), along with a mesoporous system exhibiting a high specific surface area (80.44 m2/g). Photoelectrochemical tests confirmed that the samples exhibited enhanced photocurrent response and lower charge transfer resistance. In the photocatalytic degradation experiment of methyl orange (MO), the optimal sample achieved complete degradation of the pollutant in just 10 min under visible light and 18 min under UV light. Free radical trapping experiments indicated that superoxide radicals ( $$\centerdot {\text{O}}_{2}^{ - }$$ ) and hydroxyl radicals (•OH) were the primary active species in the degradation process.