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.