NaOH-assisted hydrothermal reduction of graphene oxide

The influence of the pH of the reaction medium on the structural characteristics of hydrothermally reduced graphene oxide, synthesized by the Tour method, has been investigated. Varying the pH of the reaction medium within the range of 8.0, 10.0 and 12.0 (adjusted with NaOH) has revealed distinct effects on the morphology and properties of the resulting reduced graphene oxide. At a pH of 8.0 the hydrothermal treatment yielded reduced graphene oxide comprising of two particle fractions with a thickness equivalent to 4-5 graphitic layers each. In contrast, pH of 10.0 resulted in two particle fractions corresponding to 2–3 and 4 layers, respectively, while pH of 12.0 produced a single fraction with a particle thickness of 0.70 nm, encompassing 3 graphitic layers. Increasing the pH led to a decrease in the average lateral size of reduced graphene oxide particles to about 8 nm. All rGOs had micro- and mesopores with a specific surface area up to 226 m²/g, showing a proportional increase in mesopores with increasing pH. Analysis of slit-like micropores revealed a minimum fractal dimension (D = 2.18) at pH = 8.0. The obtained results provide valuable insights into tailoring the structural properties of hydrothermally reduced graphene oxide by controlling the pH of the reaction medium, offering potential applications in various fields, including nanotechnology and materials science.