Synthesis and Characterization of Porous Carbon/Nickel Oxide Nanocomposites for Gas Storage and Negatronic Devices

Porous organic/inorganic nanocomposites were synthesized by sol–gel technique after the incorporation of nickel oxide (NiO) nanoparticles in carbon composite based on pyrogallol and formaldehyde (PF) using picric acid as catalyst. After a drying step, the samples were heated during 2 h at different pyrolysis temperatures from 600 to 1000 °C in tubular furnace under nitrogen atmosphere. The XRD pattern exhibit that PF composite is amorphous even after thermal treatment at 1000 °C. On the other hand, the PF/NiO nanocomposites are crystallized with the appearance of the graphite structure at high pyrolysis temperature. The gas adsorption capacities for CO2 indicate that the PF composite has a tendency to adsorb CO2 higher than PF/NiO nanocomposite. In fact, the maximum value of capacity is of the order 7.5 mmol/g in PF composite and 6.5 mmol/g in PF/NiO nanocomposite. The dc conductivity shows the dominance of percolation phenomenon and explained by two models; the three dimensions variable range hopping and the nearest neighbor hopping. The voltage–current V(I) characteristics show the presence of negative differential resistance at room measurement temperature in PF/NiO-625 °C sample. The ac conductance is attributed to different origins, so it is decried by two models, like hopping conduction mechanism in PF-675 °C composite and small polaron hopping model in PF/NiO-625 °C nanocomposite.