Comparative analysis of structural, physicochemical, and electrochemical properties of graphene oxide derived from commercial graphite and rice husk biomass for sensing applications

This study presents a sustainable route to synthesize graphene oxide (GO) from rice husk biochar (RHB) without hazardous HF/NaOH pretreatment, using a modified Hummers' method. We showed that natural silicate minerals in RHB significantly alter the structure and properties of rice husk-derived GO (RHGO), reducing its electrochemical sensing performance compared to commercial graphite-derived GO (CGGO). Importantly, we demonstrated that a simple, eco-friendly process, decantation followed by electrodeposition, can reduce the adverse effects of silica in RHGO, boosting its sensing performance without needing traditional desilication methods. XPS analysis revealed that RHGO exhibited a higher silicon content of 28 % and oxygen content of 59 %, along with a lower carbon content of 12 %. In contrast, CGGO contained no silicon, 35 % oxygen, and 61 % carbon. These compositional differences indicate that CGGO had a typical GO structure, while RHGO reflected a hybrid SiO2-GO structure. RHGO also showed a larger BET surface area of 83 m2/g and a total pore volume of 0.12 cm3/g, whereas CGGO displayed a surface area of 31 m2/g and a pore volume of 0.02 cm3/g. Electrochemical tests revealed that silicates in RHGO reduced surface functionality and electron transfer between the RHGO carbon paste electrode (CPE) and ferro/ferricyanide ions in KCl solution. However, decantation and electrodeposition of RHGO onto CPE enhanced the peak current by 1.5 times, reduced the peak-to-peak separation by 1.75-fold, and reduced the charge-transfer resistance by 2.6-fold compared with bare CPE, thereby improving electron-transfer kinetics and sensing response. However, CGGO still outperformed RHGO, showing residual silicate effects persist.