Peach Pit-Activated Carbons: Effect of Row Material Form and Pyrolysis Parameters on Hydrogen Adsorption Storage

The production of activated carbons (ACs) starting from economic precursors using eco-sustainable synthesis processes appears to be a particularly interesting research field. A possible application can be represented by the use of waste materials to produce ACs through synthesis processes with a low environmental impact for hydrogen (H2) storage. In this work, ACs were produced starting from peach pits, through two processes, i.e., carbonization and physical activation of the raw material. The key process parameters (gas type and temperature) and the starting form of biomass were modified to evaluate their influence on the structural properties and, consequently, the H2 adsorption capacity. The chemical and morphological properties of the ACs were investigated through different analyses (energy-dispersive X-ray, EDX; X-ray diffraction, XRD; Fourier-transform infrared spectroscopy, FTIR; scanning electron microscopy, SEM), while textural features and adsorption capacities were determined using a volumetric apparatus. Optimization of the synthesis process allowed us to obtain ACs with a highly microporous structure (≃85%), a specific surface area of around 1317 m2/g, a total pore volume of 0.60 cm3/g, an excellent H2 adsorption capacity at low pressure (1.85 wt % at 77 K up to 1 bar), an interesting H2 adsorption capacity at high pressure (3.45 wt % at 77 K up to 80 bar), and an excellent cyclicality of storage processes but reduced storage capacity at room temperature (0.28 wt % up to 80 bar).