title: Quantitative correlation between defect density and heterogeneous electron transfer rate of single layer graphene.
abstract: Improving electrochemical activity of graphene is crucial for its various applications, which requires delicate control over its geometric and electronic structures. We demonstrate that precise control of the density of vacancy defects, introduced by Ar(+) irradiation, can improve and finely tune the heterogeneous electron transfer (HET) rate of graphene. For reliable comparisons, we made patterns with different defect densities on a same single layer graphene sheet, which allows us to correlate defect density (via Raman spectroscopy) with HET rate (via scanning electrochemical microscopy) of graphene quantitatively, under exactly the same experimental conditions. By balancing the defect induced increase of density of states (DOS) and decrease of conductivity, the optimal HET rate is attained at a moderate defect density, which is in a critical state; that is, the whole graphene sheet becomes electronically activated and, meanwhile, maintains structural integrity. The improved electrochemical activity can be understood by a high DOS near the Fermi level of defective graphene, as revealed by ab initio simulation, which enlarges the overlap between the electronic states of graphene and the redox couple. The results are valuable to promote the performance of graphene-based electrochemical devices. Furthermore, our findings may serve as a guide to tailor the structure and properties of graphene and other ultrathin two-dimensional materials through defect density engineering.
authors.affiliation: State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, and Department of Chemistry, College of Chemistry and Chemical Engineering, and ‡Department of Physics, Laboratory of Nanoscale Condensed Matter Physics, Xiamen University , Xiamen 361005, China.
authors.forename: Jin-Hui
authors.initials: JH
authors.lastname: Zhong
authors.forename: Jie
authors.initials: J
authors.lastname: Zhang
authors.forename: Xi
authors.initials: X
authors.lastname: Jin
authors.forename: Jun-Yang
authors.initials: JY
authors.lastname: Liu
authors.forename: Qiongyu
authors.initials: Q
authors.lastname: Li
authors.forename: Mao-Hua
authors.initials: MH
authors.lastname: Li
authors.forename: Weiwei
authors.initials: W
authors.lastname: Cai
authors.forename: De-Yin
authors.initials: DY
authors.lastname: Wu
authors.forename: Dongping
authors.initials: D
authors.lastname: Zhan
authors.forename: Bin
authors.initials: B
authors.lastname: Ren