Differentiate the pseudocapacitance and double-layer capacitance contributions for nitrogen-doped reduced graphene oxide in acidic and alkaline electrolytes

• Published in: Journal of power sources 2013-04, Vol.227, p.300-308
• Main Authors: Lee, Ying-Hui, Chang, Kuo-Hsin, Hu, Chi-Chang
• Format: Article
• Language: English
• Subjects: Applied sciences; Aqueous electrolyte; Capacitors. Resistors. Filters; Double-layer capacitance; Electrical engineering. Electrical power engineering; Exact sciences and technology; N-doped reduced graphene oxide; Nitrogen-containing functional group; Pseudocapacitance; Various equipment and components
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2012.11.026

Nitrogen-doped reduced graphene oxide (N-RGO) and reduced graphene oxide (RGO) have been synthesized by microwave-assisted hydrothermal method to discern the actual contribution of nitrogen-containing functional groups on the specific capacitance (CS,T) in acidic and alkaline electrolytes. Material characterization reveals similar porosity, electrolyte-accessible surface area, element composition, and graphitic crystallinity between N-RGO and RGO except the difference in the nitrogen content. In 1 M H2SO4, additional pseudocapacitance provided by pyridinic-N and pyrrolic-N/pyridone-N is clearly observed at the potential negative to 0.6 V (vs. RHE) while this contribution in pseudocapacitance diminishes in 1 M KOH due to the lack of proton in the electrolyte for these basic functional groups to undergo redox reactions. The double-layer capacitance of N-RGO in 1 M H2SO4 in higher than that in 1 M KOH owing to the presence of N-containing functional groups which increase the electronic charge density of graphene and favor proton adsorption in the acidic electrolyte. The contribution of nitrogen-containing functional groups on CS,T in acidic media is more pronounced than that in the alkaline electrolyte. This finding is crucial for the future application of N-doped carbons in supercapacitors to achieve full utilization. [Display omitted] In 1 M H2SO4, additional pseudocapacitance provided by pyridinic-N and pyrrolic-N is clearly observed at the potential negative to 0.6 V (vs. RHE) while this contribution in pseudocapacitance diminishes in 1 M KOH due to the lack of proton in the electrolyte for these basic functional groups to undergo redox reactions. The presence of N-containing functional groups also results in higher double-layer capacitance of N-RGO in 1 M H2SO4 than that in 1 M KOH owing to the increased electronic charge density favors the proton adsorption in the acidic electrolyte. The contribution of nitrogen-containing functional groups on specific total capacitance in acidic solution is more pronounced than in the alkaline electrolyte. ► The effects of N-doped groups are more pronounced in acids than in alkaline media. ► Pseudocapacitance from pyridinic-/pyrrolic-N is observed negative to 0.6 V in acids. ► Nitrogen-doped groups contribute higher Cdl in H2SO4 compared to that in KOH. ► N-RGO as anodes in both acidic and alkaline media results in high specific energy.