Tailorable Ultrathin Copper Oxysulfide for Room-Temperature, Reversible, and Selective Hydrogen Sulfide Sensing

Accurate, low-cost, and energy-efficient detection of hydrogen sulfide (H₂S) is vital for industries such as petroleum, natural gas, and wastewater treatment. While chemiresistive sensors are well suited for this purpose, traditional metal oxides typically require high operating temperatures (>100 °C) or external stimuli (e.g., UV light) for activation. In this work, we introduce two-dimensional (2D) copper oxysulfide nanoflakes (∼10 nm thick) as a novel material for room-temperature, reversible, and selective H₂S sensing. These 2D copper oxysulfides, synthesized via the calcination of copper sulfide under both oxygen-deficient and oxygen-rich conditions, show significant changes in crystal structure and electronic band properties compared to copper sulfide while retaining p-type semiconducting behavior. This alteration enables efficient interfacial charge transfer with adsorbed H₂S molecules. The oxygen-rich copper oxysulfide exhibits a response magnitude of 143% for 2 ppm of H₂S in air at room temperature, with a linear response across concentrations ranging from 0.25 to 2 ppm. Furthermore, the sensor demonstrates complete reversibility, excellent selectivity, and high stability. This work presents a promising strategy for high-performance room-temperature H₂S sensing utilizing metal oxysulfides as an emerging class of materials derived from metal oxides and sulfides.