Abstract In recent years, ferrites have emerged as a promising option for sensing reducing, oxidizing, toxic, an‎d flammable gases, owing to their long-term stability an‎d superior selec‎tivity compared to other materials. Hydrogen gas H2 , one such gas, is considered highly hazardous due to its specific characteristics, including being odorless, colorless, tasteless (imperceptible to human senses), an‎d highly explosive. Therefore, the development of gas sensors is of paramount importance for ensuring safety, detecting the presence, an‎d controlling the concentration of this gas in the environment. Consequently, this research focuses on investigating the sensing properties of hydrogen gas sensors based on Cobalt Ferrite-Reduced Graphene Oxide nanocomposites (CoFe2 O4 -RGO) an‎d Palladium-Doped Cobalt Ferrite (CoFe2 O4 -Pd). Specifically, the effect of incorporating varying weight percentages of RGO an‎d Pd on the gas sensing characteristics of Cobalt Ferrite( CoFe2 O4 ) is examined. Initially, Cobalt Ferrite nanoparticles were synthesized via the self-combustion method, followed by their compositing with different weight percentages of RGO an‎d Pd. XRD patterns confirmed the formation of a single-phase cubic spinel ferrite structure. Furthermore, SEM images illustrated the sheet-like presence of graphene within the nanocomposites. The XPS spectrum clearly revealed the presence of Co, Fe, O, an‎d Pd elements in the composition. It was also observed that the sensing response of the samples decreased with compositing an‎d increasing the weight percentage of RGO. The maximum hydrogen gas sensitivity for all samples occurred at a temperature of 350°C. The incorporation of Pd onto Cobalt Ferrite demonstrated that the sensor response improves with an increase in Pd catalyst loading (up to 0.075wt%), but a decrease in response is observed beyond this concentration. Thus, the Cobalt Ferrite sample doped with 0.075wt% Palladium exhibited the highest sensitivity to hydrogen gas, with a 200% response among all fabricated samples. In the investigation of concentration effects on sensing, an increase in the hydrogen gas concentration led to a corresponding increase in the sensor response for all samples. All samples demonstrated acceptable repeatability an‎d stability over 5 consecutive cycles at 350°C under a 10% H2 concentration. Moreover, doping Cobalt Ferrite with Palladium resulted in a reduction in response time an‎d, particularly, recovery time. The CoFe2 O4 - 0.05%Pd sample achieved the best response time (71seconds) an‎d recovery time (3seconds) at 350°C. The results of this investigation indicate that Palladium-doped Cobalt Ferrite possesses significant potential for application in gas sensing devices

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مهدي رنجبر

حميده شاكري پور , اسماعيل عبدالحسيني سارسري