Preparation of N-doped graphite oxide for supercapacitors by NH3 cold plasma

In this work, N-doped graphite oxide (GO-P) was prepared by cold plasma treatment of GO using a mixture of NH3 and Ar as the working gas. When the ratios of NH3:Ar were 1:2, 1:3, and 1:4, the specific capacitances of the GO-P(NH3:Ar = 1:2), GO-P(NH3:Ar = 1:3), and GO-P(NH3:Ar = 1:4) were 124.5, 187.7, and 134.6 F center dot g(-1), respectively, which were 4.7, 7.1, and 5.1 times that of GO at the current density of 1 A center dot g(-1). The capacitance retention of the GO-P(NH3:Ar = 1:3) was 80% when it was cycled 1000 times. The characterization results showed that the NH3 cold plasma could effectively produce N-doped GO and generate more active defects. The N/C ratio and the contents of pyridinic nitrogen and graphitic nitrogen of the GO-P(NH3:Ar = 1:3) were the highest. These were conducive to providing pseudocapacitance and reducing the internal resistance of the electrode. In addition, the I (D)/I (G) of the GO-P(NH3:Ar = 1:3) (1.088) was also the highest, indicating the highest number of defects. The results of discharge parameters measurement and in situ optical emission spectroscopy diagnosis of NH3 plasma showed that the discharge is the strongest when the ratio of NH3:Ar was 1:3, thereby the generated nitrogen active species can effectively promote N-doping. The N-doping and abundant defects were the keys to the excellent electrochemical performance of the GO-P(NH3:Ar = 1:3). NH3 cold plasma is a simple and rapid method to prepare N-doped GO and regulate the N-doping to prepare high-performance supercapacitors.