Carbon nanoflowers for hydrogen storage and air purification applications

Nanostructured carbon materials with controlled porosity and surface chemistry represent highly promising solutions for both hydrogen (H2) storage and environmental remediation applications. In this work, four carbon nanoflower (CNF) samples were synthesized via free-radical polymerization of acrylonitrile, followed by stabilization, carbonization and chemical activation with KOH, leading to hierarchical nanoporous structures with tunable physicochemical properties [1]. Comprehensive characterization was performed using N2 adsorption at 77 K, H2 adsorption (up to 100 bar at 77 K and 298 K), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The CNF materials exhibited very high specific surface areas of up to ~3000 m2 /g and total pore volumes up to ~1.3 cm3 /g, with dominant microporosity (80-92 %) and narrow pore size distributions (1.1-1.2 nm), features that are particularly favorable for gas adsorption. H2 storage measurements revealed uptakes of up to ~2.5 wt.% at 77 K and 1 bar, while at higher pressures the maximum excess uptake reached ~5.6 wt.% at 77 K and ~35 bar and the total storage capacity reached ~8.2 wt.% at 77 K and ~95 bar, confirming the high adsorption performance of the materials. A positive relationship between micropore volume and H2 uptake was observed, highlighting the critical role of narrow microporosity in governing H2 storage performance. XPS analysis indicated the presence of heteroatoms (O, N), which may enhance surface interactions and contribute to the adsorption of hazardous organic compounds. In this respect, the CNF materials showed strong potential for air purification applications, including the removal of toxic vapors. In particular, towards vapors of a mustard gas simulant, the best performing CNF exhibited showed a gravimetric update reaching 1.4 times its own mass (1400 mg/g), with limited desorption, indicating strong adsorption. Finally, a multivariate analysis integrating textural properties, surface composition, H2 uptake and mustard gas removal performance was carried out to assess similarities among the CNF materials and to identify the key features governing their separation. Overall, carbon nanoflowers emerge as efficient and versatile material platforms that bridge clean energy and environmental protection applications, offering significant potential for advanced adsorption-based systems.