In-situ sulfidation strategy for constructing SnO2/SnS2 heterojunctions: Achieving highly robust flexible room temperature H2S sensors

The development of portable, low-power H 2 S sensors is critical for environmental safety but remains challenged to balance high sensitivity with mechanical flexibility at room temperature. Herein, we present a hierarchical SnO 2 /SnS 2 nanoflower composite synthesized via a facile in-situ sulfidation strategy, which ensures intimate lattice coherence for robust flexible sensing. The optimal sensor on a PET substrate exhibits a high response of 19.01 to 10 ppm H 2 S at 25 °C, a low theoretical detection limit of 95.38 ppb, and excellent mechanical stability under 90° bending. Mechanistically, Mott-Schottky analysis confirms that SnO 2 /SnS 2 heterojunctions induce a 50-fold increase in carrier concentration. This electronic modulation extends the Debye length (24.4 nm) beyond the average crystallite size (16.9 nm), creating a volume depletion state in ambient air that enables massive resistance modulation upon H 2 S exposure. This work demonstrates a robust flexible sensor and establishes a quantitative criterion for heterojunction design through Debye length engineering.