Electronic structures of graphene oxide (GO) and hydro-thermally reduced graphene oxides (rGOs) processed at low temperatures (120–180°C) were studied using X-ray absorption near-edge structure (XANES), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS). C K-edge XANES spectra of rGOs reveal that thermal reduction restores C = C sp2 bonds and removes some of the oxygen and hydroxyl groups of GO, which initiates the evolution of carbonaceous species. The combination of C K-edge XANES and Kα XES spectra shows that the overlapping π and π* orbitals in rGOs and GO are similar to that of highly ordered pyrolytic graphite (HOPG), which has no band-gap. C Kα RIXS spectra provide evidence that thermal reduction changes the density of states (DOSs) that is generated in the π-region and/or in the gap between the π and π* levels of the GO and rGOs. Two-dimensional C Kα RIXS mapping of the heavy reduction of rGOs further confirms that the residual oxygen and/or oxygen-containing functional groups modify the π and σ features, which are dispersed by the photon excitation energy. The dispersion behavior near the K point is approximately linear and differs from the parabolic-like dispersion observed in HOPG.
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机译:使用X射线吸收近边缘结构(XANES),X射线发射光谱法研究了在低温(120–180°C)下加工的氧化石墨烯(GO)和水热还原氧化石墨烯(rGOs)的电子结构。 XES)和共振非弹性X射线散射(RIXS)。 rGO的C K边缘XANES光谱表明,热还原可恢复C = C sp 2 sup>键,并除去GO中的一些氧和羟基,从而引发了碳质物种的演化。 C K-edge XANES和KαXES光谱的组合表明,rGOs和GO中的π和π*轨道重叠,类似于无带隙的高阶热解石墨(HOPG)。 CKαRIXS光谱提供的证据表明,热还原改变了GO和rGO的π区域和/或π和π*能级之间的间隙中产生的态密度(DOS)。 rGOs的大量还原的二维CKαRIXS映射进一步证实,残余的氧和/或含氧官能团修饰了π和σ特征,这些特征被光子激发能分散。 K点附近的色散行为近似线性,与HOPG中观察到的类似抛物线的色散不同。
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