Phase-Engineered 1T/2H-MoS2/SnS p-n Heterointerfaces for Enhanced Piezocatalytic Sulfamethoxazole Degradation

Piezocatalytic conversion of mechanical energy into chemical reactivity is attractive for water treatment, but rapid recombination limits strain-induced carrier utilization. Here, a phase-engineered 1T/2H-MoS2/SnS p-n heterojunction integrated metallic-phase conduction, interfacial charge redistribution, and piezoelectric polarization. Structural, electromechanical, electrochemical, spectroscopic, and theoretical analyses resolved the structure-interface-activity relationship. The heterostructure exhibited an effective d33 of approximately 15.6 pm/V, nearly 3-fold that of 2H-MoS2. Under ultrasound (40 kHz, 150 W), 10 mg catalyst removed 96.6% of sulfamethoxazole (5 mg/L, 100 mL) within 30 min after 60 min dark equilibration. The apparent first-order rate constant was 0.113 min-1, which was 16.76, 8.77, and 2.04 times those of 2H-MoS2, 1T/2H-MoS2, and 2H-MoS2/SnS, respectively. Binding-energy shifts, surface-potential contrast, impedance measurements, and theoretical calculations supported interfacial charge redistribution and oxygen activation. Scavenging and electron paramagnetic resonance measurements identified singlet oxygen as the dominant oxidant, with superoxide and hydroxyl radicals as secondary species. Total organic carbon removal reached 59% in ultrapure water and exceeded 45% in spiked real-water matrices, while sulfamethoxazole removal remained above 92%. Structure-based screening predicted lower aquatic toxicity than sulfamethoxazole for most tentative transformation products, although several showed the opposite trend. This pattern suggests possible toxicity reduction during degradation but does not establish treated-solution detoxification. The catalyst retained approximately 85% of its initial activity after five cycles. These results establish interfacial-field coupling as a design principle for layered piezocatalysts.