In this report, spinel ZnMn2O4 microspheres (ZMO) were synthesized via a hydrothermal method. Then nanocomposites based on DBSA doped-Polypyrrole nanofibers assisted by various wt% of ZMO (PZMs) have been synthesized by a chemical polymerization method. The results showed the formation of microspherical morphology for the tetragonal phase of the ZMO, and the decoration of the ZMOs with DBSA doped-Polypyrrole nanofibers in the nanocomposites with high specific surface area and porosity. The H2 gas sensing properties of the PZMs films were investigated under different concentrations of H2 gas at room temperature, ambient pressure (1 atm), and relative humidity (35%) for the first time. The results showed as the wt% of metal oxide increased from 5 to 30%, the gas sensing response decreased from 1.32 to 1.09, while t_res increased from 108 to 143 s, respectively, toward 15,000 ppm H2 gas. A sample with 5 wt% ZMO (PZM5) showed not only the best response and t_res between the samples at dynamic conditions but also excellent long-term stability after 6 months with about 3% variation than the initial experiment. Different percentages of humidity presented a change (1.3–11.3)% in the results of gas sensing response at H2 gas different concentrations. The suitable response and t_res at dynamic situations along with significant long-term stability and good selectivity offer our hand-made sensing layers as a reliable device for H2 gas sensing with a broad-wide application. Finally, the possible mechanism of the H2 sensing in the PZMs was discussed in detail.
