Quality Improvement of Few-Layers Defective Graphene from Biomass and Application for H2 Generation

Abstract

Pyrolysis of filmogenic natural polymers gives rise to the formation of films of few-layers defective, undoped, and doped graphenes with low electrical conductivity (3000 to 5000 Ω/sq). For the sake of valorization of biomass wastes, it would be of interest to decrease the density of structural defects in order to increase the conductivity of the resulting few-layers graphene samples. In the present study, analytical and spectroscopic evidence is provided showing that by performing the pyrolysis at the optimal temperature (1100 °C), under a low percentage of H2, a significant decrease in the density of defects related to the presence of residual oxygen can be achieved. This improvement in the quality of the resulting few-layers defective graphene is reflected in a decrease by a factor of about 3 or 5 for alginic acid and chitosan, respectively, of the electrical resistance. Under optimal conditions, few-layers defective graphene films with a resistance of 1000 Ω /sq were achieved. The electrode made of high-quality graphene prepared at 1100 °C under Ar/H2 achieved a H2 production of 3.62 µmol with a positive applied bias of 1.1 V under LED illumination for 16 h.

3D defective graphenes with subnanometric porosity obtained by soft-templating following zeolite procedures

“…Besides micro-and ultra microporosity with a dened subnanometric pore size and high surface area, the templating effect of CTAC on SA was clearly evidenced by recording a set of scanning electron microscopy (SEM) images upon treatment of the CTAC-SA solid at increasing temperatures in the range from 300 to 900 C. Note that previous studies have determined that pyrolysis of SA at temperatures of 1200 C results in the volatilization of all the material. 32 These images reveal that the CTAC-SA material was constituted by spheres, coated by thin lms. By adjusting the CTAC-SA mass ratio to an optimal value (weight ratio about 1), the solid was constituted mainly by spheres of about 1.7 mm diameter and the amount of residual lm coating the spheres notably decreased.…”

Design, Fabrication, and Mechanism of Nitrogen‐Doped Graphene‐Based Photocatalyst

“…In particular, the synthesis of NG by biomass pyrolysis has been frequently reported and is expected to be applied to the large‐scale production. [ 109–112 ] For instance, Primo et al. [ 113 ] synthesized high‐quality monolayer NG by the pyrolysis of biomass waste (chitosan) at 800 °C.…”

Production and Applications of Biomass-Derived Graphene-Like Materials

“…On the other hand, He and teammates [51] have established the preparation of graphene using chitosan as natural polysaccharides via pyrolysis under H 2 gas to reduce the defects on graphene. Oxygen functionality is known as one type of defect because it will deteriorate the graphene electrical conductivity.…”

“…Fig. 11 Raman analysis of chitosan-derived graphene at different conditions [51] with increased total pore volume, 1.28 cm 3 /g. The adsorption-desorption isotherm shows that typical type IV isotherm is obtained which shows that the N 2 adsorption quantity increases with relative pressures (Fig.…”