Effect of nitrogen doping on the structure and electrochemical properties of vertical graphene sheets prepared by HWP-CVD.

3D nitrogen-doped vertically-oriented graphene nanosheets (3D N/VGs) were controllably prepared by helicon wave plasma chemical vapor deposition (HWP-CVD) employing argon, methane, and nitrogen by varying the N 2 flow rate (R N2) without any catalyst and substrate heating during the growth. The effect of plasma gas phase species on the growth structure of N/VGs thin films was studied. The influence of nitrogen doping content on the structure and properties of VGs was analyzed. A growth model for the preparation of N/VGs by HWP-CVD was proposed. The results show that the elevated doping content of nitrogen atoms promotes enhanced CH 4 dissociation and access to more H atoms, leading to an elevated nanosheet number density and a reduced growth rate. More excited N atoms could be embedded into the C vacancy to replace the missing C atom and restore the hexagonal network and increasing the nitrogen content. N/VGs with lower defect densities obtained with enhanced doping of nitrogen. The effective average distance between defects increases with nitrogen content, and the tunneling phenomenon is apparent, increasing resistance. Electrochemical performance tests showed that VGs with high nitrogen atomic content have higher specific capacitance and rate performance, up to 1340 μF/cm2 and 91.7%, respectively. • One step synthesis of N/VGs by CH 4 /N 2 HWP-CVD. • Preparation of N/VGs by doping with controllable N atom concentration. • The doping of N atoms improves the electrochemical performance of VGs. • The substitution of nitrogen atoms for carbon atoms forms C–N bonds, which improves the wall spacing and wall structure size of VGs. [ABSTRACT FROM AUTHOR]