Tuning quantum capacitance in 2D graphene electrodes: the role of defects and charge carrier concentration

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2023-05, Vol.11 (19), p.631-635
• Main Authors: Hassan, Ayaz, Mattioli, Isabela A, Colombo, Rafael N. P, Crespilho, Frank N
• Format: Article
• Language: English
• Subjects: Aqueous electrolytes; Capacitance; Carrier density; Current carriers; Defects; Electrodes; Electronic properties; Graphene; Monolayers; Oxidation; Tuning
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/d2tc04037a

Even though graphene has been intensively applied in electrochemical devices, the effects of oxidation and how the presence of graphene structural defects interferes with the monolayer graphene electrode-aqueous electrolyte interface remains unclear. Here, we investigate the role of structural defects in the quantum capacitance at the interface between a graphene monolayer and the aqueous electrolyte solution, where the graphene was gradually oxidized by a temporal-controlled electrochemical procedure. We show that the quantum capacitance of graphene can be modulated by tuning the electronic properties, which resulted in a three-fold increase from a value of 3.83 μF cm −2 for the pristine graphene up to 11.11 μF cm −2 for the structurally modified monolayers. A strong correlation is observed between the carrier concentration, density of defects, and quantum capacitance. We suggest that the control of such properties can modulate the performance of graphene-based electrochemical devices according to application. Electrochemical oxidation of a graphene monolayer results in a G-band shift in the micro-Raman spectrum and an increase in the quantum capacitance, resulting from an increase in the number and density of defects and charge carrier concentration in the graphene structure.