Noble-metal-free hydrogen sensor based on cobalt-doped zinc ferrite/reduced graphene oxide for room-temperature operation with wide concentration detection

Resistive hydrogen sensors based on semiconducting metal oxides offer high sensitivity but are often limited by high operating temperatures and insufficient selectivity. Herein, a noble-metal-free nanocomposite of cobalt-doped zinc ferrite and reduced graphene oxide was developed for room-temperature hydrogen sensing. Porous cobalt-doped zinc ferrite microspheres were synthesized and subsequently integrated in situ with reduced graphene oxide, followed by comprehensive structural and surface characterization. The optimized composite delivered a response of 3.58 to 10000 ppm H₂ at 25 °C with response/recovery times of 27/85.7 s. The sensor exhibited a detectable response down to 5 ppm H₂ (lowest tested concentration), showed good selectivity against common interfering vapors, and retained >95% of its initial response after 30 days. The enhanced performance is attributed to the synergistic coupling between cobalt-induced defect modulation and the conductive reduced graphene oxide network, which promotes efficient charge transfer and surface reactivity at room temperature.