High surface area carbon nitride nanotubes for improved hydrogen storage: A grinding and solution mixing approach

This study examines the structural, chemical, and hydrogen storage properties of graphitic carbon nitride (g-C 3 N 4 ) nanotubes synthesized via a novel grinding-solution-synthesis (GSS) method which involve two consecutive precursor mixing processes: grinding and solution mixing. The impact of grinding duration on morphology, surface area, and hydrogen storage capacity was analyzed. X-ray diffraction (XRD) confirmed characteristic (100) and (002) peaks at ∼13.1° and 28.0°, respectively. Fourier-transform infrared (FTIR) spectroscopy identified tri-s-triazine heterocycles and hydrogen-bonded amino groups, with a new peak at 1650 cm −1 suggesting structural modifications. X-ray photoelectron spectroscopy (XPS) confirmed elemental composition with minor bonding variations. Nitrogen adsorption/desorption analyses showed that the 30-min ground sample (B1G30) had the highest specific surface area (321 m 2 g -1 ) and pore volume (1.07 cm 3 /g), while prolonged grinding (60–90 min) caused nanotube degradation, reducing these properties. Scanning and transmission electron microscopy (SEM/TEM) confirmed nanotubular morphology, with decreasing diameters and increasing structural collapse at longer grinding durations. Hydrogen storage tests revealed B1G30 exhibited the highest capacity (0.81 wt% at 3.7 MPa), decreasing with extended grinding (B1G60: 0.79 wt%, B1G90: 0.75 wt%) due to structural collapse. Extrapolated data suggested B1G30 could reach ∼4.0 wt% at 10 MPa. These findings underscore the importance of nanotube integrity in optimizing hydrogen adsorption and highlight g-C 3 N 4 nanotubes’ potential for hydrogen storage applications. This GSS technique presents a cost-effective method for industrial-scale fabrication of high-surface-area g-C 3 N 4 nanotubes, enabling their large-scale use in energy storage, carbon capture, photocatalysis, and other applications. • Grinding-solution-synthesis was used to fabricate g-C 3 N 4 nanotubes for hydrogen storage applications. • 30-minute grinding yielded g-C 3 N 4 nanotubes with optimal surface area and hydrogen storage capacity. • Achieved surface area of 321 m 2 /g and hydrogen storage capacity of 0.81 wt% under tested conditions. • Nanotubes showed fast hydrogen adsorption/desorption kinetics (<2 min), enabling quick refuelling. • Extrapolated storage capacity reached ∼ 4.0 wt% at 10 MPa, nearing DOE’s 5.5 wt% target at 12 MPa.