Room-temperature response of MOF-derived Pd@PdO core shell/γ-Fe₂O₃ microcubes decorated graphitic carbon based ultrasensitive and highly selective H₂ gas sensor

With the current upsurge in hydrogen economies all over the world, an increased demand for improved chemiresistive H₂ sensors that are highly responsive and fast acting when exposed to gases is expected. Owing to safety concerns about explosive and highly flammable H₂ gas, it is important to develop resistive sensors that can detect the leakage of H₂ gas swiftly and selectively. Currently, interest in metal-organic frameworks (MOFs) for gas-sensor applications is increasing due to their open-metal sites, large surface area, and unique surface morphologies. In this research, a highly selective and sensitive H₂-sensor was established based on graphitic carbon (GC) anchored spherical Pd@PdO core-shells over γ-Fe₂O₃ microcube (Pd@PdO/γ-Fe₂O₃@GC which is termed as S3) heterostructure materials. The combined solvothermal followed by controlled calcination-assisted S3 exhibited a specific morphology with the highest surface area of 79.12 m² g⁻¹, resulting in fast response and recovery times (21 and 29 s, respectively), and excellent sensing performance (ΔR/R₀ ∼ 96.2 ± 1.5), outstanding long-term stability, and a 100 ppb detection limit when detecting H₂-gas at room temperature (mainly in very humid surroundings). This result proves that adsorption sites provided by S3 can promote surface reactions (adsorption and desorption) for ultrasensitive and selective H₂ gas sensors.