Identifying the Active Site in Nitrogen-Doped Graphene for the VO2+/VO2+Redox Reaction

作者：Jutao Jin, Xiaogang Fu, Qiao Liu, Yanru Liu, Zhiyang Wei, Kexing Niu, Junyan Zhang · 发表于：ACS Nano · 年份：2013 · DOI：10.1021/nn3046709 · 被引用次数：268 · 研究领域：Advanced battery technologies research、Electrocatalysts for Energy Conversion、Supercapacitor Materials and Fabrication

Nitrogen-doped graphene sheets (NGS), synthesized by annealing graphite oxide (GO) with urea at 700-1050 °C, were studied as positive electrodes in a vanadium redox flow battery. The NGS, in particular annealed at 900 °C, exhibited excellent catalytic performance in terms of electron transfer (ET) resistance (4.74 ± 0.51 and 7.27 ± 0.42 Ω for the anodic process and cathodic process, respectively) and reversibility (ΔE = 100 mV, Ipa/Ipc = 1.38 at a scan rate of 50 mV s(-1)). Detailed research confirms that not the nitrogen doping level but the nitrogen type in the graphene sheets determines the catalytic activity. Among four types of nitrogen species doped into the graphene lattice including pyridinic-N, pyrrolic-N, quaternary nitrogen, and oxidic-N, quaternary nitrogen is verified as a catalytic active center for the [VO](2+)/[VO2](+) couple reaction. A mechanism is proposed to explain the electrocatalytic performance of NGS for the [VO](2+)/[VO2](+) couple reaction. The possible formation of a N-V transitional bonding state, which facilitates the ET between the outer electrode and reactant ions, is a key step for its high catalytic activity.